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<h1 id="容器和Java-web"><a href="#容器和Java-web" class="headerlink" title="容器和Java web"></a>容器和Java web</h1><h4 id="一、java-web容器规范"><a href="#一、java-web容器规范" class="headerlink" title="一、java web容器规范"></a>一、java web容器规范</h4><h5 id="1、概念"><a href="#1、概念" class="headerlink" title="1、概念"></a>1、概念</h5><ul>
<li>web容器是能部署web应用程序的环境</li>
<li>Tomcat容器是Java Servlet，JavaServer Pages，Java Expression Language和Java WebSocket（Java EE）技术实现</li>
<li>Servlet是主要作用是给上级容器(Tomcat)等提供doGet()和doPost()等方法。其生命周期实例化、初始化、调用、销毁受控于Tomcat容器</li>
<li>Java Web应用由一组Servlet、HTML页、类、以及其它可以被绑定的资源构成。它可以在各种web容器(如Tomcat)中运行。</li>
</ul>
<h4 id="二、Servlet"><a href="#二、Servlet" class="headerlink" title="二、Servlet"></a>二、Servlet</h4><ul>
<li>Servlet本质上市一个java类，按照规范可以在javaweb容器中运行，对客户端的请求做出响应。</li>
</ul>
<h5 id="2-1、Servlet的生命周期"><a href="#2-1、Servlet的生命周期" class="headerlink" title="2.1、Servlet的生命周期"></a>2.1、Servlet的生命周期</h5><ul>
<li>init()初始化，数据初始化 </li>
<li>service()方法处理请求调用的实际方法，请求后把结果返回给客户端，service() 方法由容器调用，service 方法在适当的时候调用 doGet、doPost、doPut、doDelete 等方法。</li>
<li>destory()方法结束请求</li>
</ul>
<figure class="highlight aspectj"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"> <span class="comment">//service方法调用特征</span></span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">void</span> service(ServletRequest request, </span><br><span class="line"> ServletResponse response) </span><br><span class="line"> <span class="keyword">throws</span> ServletException, IOException{</span><br><span class="line">}</span><br><span class="line"> <span class="comment">//调用service之后常见的doGet doPost方法</span></span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">void</span> doGet(HttpServletRequest request,</span><br><span class="line"> HttpServletResponse response)</span><br><span class="line"> <span class="keyword">throws</span> ServletException, IOException {</span><br><span class="line"> <span class="comment">// 处理</span></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="2-2、Servlet-demo"><a href="#2-2、Servlet-demo" class="headerlink" title="2.2、Servlet demo"></a>2.2、Servlet demo</h5><ul>
<li><p>流程</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line"> <span class="keyword">import</span> java.io.*;</span><br><span class="line"><span class="keyword">import</span> javax.servlet.*;</span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.*;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">SampileServlet</span> <span class="keyword">extends</span> <span class="title">HttpServlet</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> String message;</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">init</span><span class="params">()</span> <span class="keyword">throws</span> ServletException</span></span><br><span class="line"><span class="function"> </span>{</span><br><span class="line"> <span class="comment">// 执行必需的初始化</span></span><br><span class="line"> message = <span class="string">" sample"</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">doGet</span><span class="params">(HttpServletRequest request,</span></span></span><br><span class="line"><span class="function"><span class="params"> HttpServletResponse response)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> ServletException, IOException</span></span><br><span class="line"><span class="function"> </span>{</span><br><span class="line"> <span class="comment">// 设置响应内容类型</span></span><br><span class="line"> response.setContentType(<span class="string">"text/html"</span>);</span><br><span class="line"> <span class="comment">// 实际的逻辑是在这里</span></span><br><span class="line"> PrintWriter out = response.getWriter();</span><br><span class="line"> out.println(<span class="string">"<h1>"</span> + message + <span class="string">"</h1>"</span>);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">destroy</span><span class="params">()</span></span></span><br><span class="line"><span class="function"> </span>{</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
</li>
<li><p>在路由层配置url映射关系，类似于spring中的RequestMapping,Python flaskweb框架中的@app.route(“/index.html”)功能</p>
</li>
</ul>
<figure class="highlight dts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="params"><web-app></span> </span><br><span class="line"><span class="params"><servlet></span></span><br><span class="line"><span class="params"><description></span><span class="params"></description></span></span><br><span class="line"><span class="params"><display-name></span>HelloServlet<span class="params"></display-name></span></span><br><span class="line"><span class="params"><servlet-name></span>HelloServlet<span class="params"></servlet-name></span></span><br><span class="line"><span class="params"><jsp-file></span>/servlet.jsp<span class="params"></jsp-file></span></span><br><span class="line"><span class="params"></servlet></span></span><br><span class="line"> <span class="params"><servlet-mapping></span></span><br><span class="line"> <span class="params"><servlet-name></span>HelloServlet<span class="params"></servlet-name></span></span><br><span class="line"> <span class="params"><url-pattern></span><span class="meta-keyword">/servlet/</span>HelloServlet<span class="params"></url-pattern></span></span><br><span class="line"><span class="params"></servlet-mapping></span></span><br><span class="line"><span class="params"><servlet></span></span><br><span class="line"><span class="params"></web-app></span></span><br></pre></td></tr></table></figure>
<h4 id="三、Cookie和Session"><a href="#三、Cookie和Session" class="headerlink" title="三、Cookie和Session"></a>三、Cookie和Session</h4><ul>
<li>Session保存在服务端，主要是服务端了标识用户而产生的，用于会话跟踪。</li>
<li>Cookie，cookie是客户端发送给服务端的，session的跟踪主要也是用cookie来实现的。cookie信息一般保存在http报文信息中。</li>
<li>在jsp中，有Cookie对象供用户调用,可以设置服务端需要的key和value</li>
</ul>
<figure class="highlight ebnf"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="attribute">Cookie cookie</span> = new Cookie(<span class="string">"key"</span>,<span class="string">"value"</span>);</span><br></pre></td></tr></table></figure>
<h4 id="四、JSP"><a href="#四、JSP" class="headerlink" title="四、JSP"></a>四、JSP</h4><ul>
<li>Java server pages一种根据服务端数据动态生成界面的技术，和很多前端模板引擎类似，jsp是一个servle程序。在界面中写入很多控制代码，来实现数据的动态渲染，之前学习过jinja2类似的模板引起，语法非常像。</li>
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<h1 id="反射，注解和动态代理，类加载"><a href="#反射，注解和动态代理，类加载" class="headerlink" title="反射，注解和动态代理，类加载"></a>反射，注解和动态代理，类加载</h1><h4 id="一、反射"><a href="#一、反射" class="headerlink" title="一、反射"></a>一、反射</h4><h5 id="1、概念"><a href="#1、概念" class="headerlink" title="1、概念"></a>1、概念</h5><ul>
<li>java的反射机制指的是程序在运行过程中，对于类，能获取到类的属性和方法，对于对象，能够调用他的属性和方法，动态的获取数据。</li>
</ul>
<h5 id="1、获取类的属性和方法"><a href="#1、获取类的属性和方法" class="headerlink" title="1、获取类的属性和方法"></a>1、获取类的属性和方法</h5><ul>
<li>假设有一个Student类，</li>
</ul>
<figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * class</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Student</span> {</span></span><br><span class="line"> <span class="keyword">public</span> String name;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">doHomeWork</span><span class="params">()</span></span>{</span><br><span class="line"> <span class="comment">//do something</span></span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<ul>
<li>获取类名和属性</li>
</ul>
<figure class="highlight monkey"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> java.lang.reflect.<span class="keyword">Field</span>;</span><br><span class="line"><span class="keyword">import</span> java.lang.reflect.Method;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Main</span> {</span></span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> static void main(String[] args) {</span><br><span class="line"> <span class="class"><span class="keyword">Class</span> <span class="title">stuClass</span> = <span class="title">Student</span>.<span class="title">class</span>;</span></span><br><span class="line"> System.out.println(stuClass.getName());</span><br><span class="line"> <span class="keyword">Field</span>[] fields = stuClass.getFields();</span><br><span class="line"> <span class="function"><span class="keyword">Method</span>[] <span class="title">methods</span> =</span> stuClass.getMethods();</span><br><span class="line"> <span class="keyword">for</span>(<span class="keyword">Field</span> <span class="keyword">field</span> : fields){</span><br><span class="line"> System.out.println(<span class="keyword">field</span>.getName());</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">for</span>(<span class="function"><span class="keyword">Method</span> <span class="title">method</span> :</span> methods){</span><br><span class="line"> System.out.println(<span class="function"><span class="keyword">method</span>.<span class="title">getName</span>(</span>));</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<ul>
<li>此外，也可以访问私有方法，通过 class.getDeclaredMethod(“privateMethod”, String.class, int.class)可以获取。</li>
</ul>
<h4 id="二、注解"><a href="#二、注解" class="headerlink" title="二、注解"></a>二、注解</h4><ul>
<li>注解可以使得Java源代码中可以添加功能性的实现代码，还可以添加元数据，和类于接口一样，注解也属于一种类型，使用@interface进行标记,比如定义一个Hello注解</li>
</ul>
<figure class="highlight css"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="selector-tag">import</span> <span class="selector-tag">java</span><span class="selector-class">.lang</span><span class="selector-class">.annotation</span><span class="selector-class">.ElementType</span>;</span><br><span class="line"><span class="selector-tag">import</span> <span class="selector-tag">java</span><span class="selector-class">.lang</span><span class="selector-class">.annotation</span><span class="selector-class">.Retention</span>;</span><br><span class="line"><span class="selector-tag">import</span> <span class="selector-tag">java</span><span class="selector-class">.lang</span><span class="selector-class">.annotation</span><span class="selector-class">.RetentionPolicy</span>;</span><br><span class="line"><span class="selector-tag">import</span> <span class="selector-tag">java</span><span class="selector-class">.lang</span><span class="selector-class">.annotation</span><span class="selector-class">.Target</span>;</span><br><span class="line"></span><br><span class="line">@<span class="keyword">Retention</span>(<span class="keyword">RetentionPolicy</span>.<span class="keyword">RUNTIME</span>)</span><br><span class="line">@<span class="keyword">Target</span>(<span class="keyword">ElementType</span>.<span class="keyword">METHOD</span>)</span><br><span class="line"><span class="keyword">public</span> @interface Hello {</span><br><span class="line"> </span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<ul>
<li>使用场景，当类，属性和对象标记注解以后，注解的信息提取使用java反射的形式，主要给编译器以及工具类型的软件使用。</li>
</ul>
<h5 id="2-1-元注解"><a href="#2-1-元注解" class="headerlink" title="2.1 元注解"></a>2.1 元注解</h5><ul>
<li>元注解是标记注解的注解，元注解可以指明注解是做什么的，常用的有：</li>
<li>@Retention 注解的保留期，取值有RetentionPolicy.SOURCE（注解在源码期间保留）， RetentionPolicy.CLASS(保留到编译进行的时候，不会加载进jvm) RetentionPolicy.RUNTIME(保留到程序运行时)</li>
<li>@Document 将注解的元素包含到java doc中</li>
<li>@Target 注解使用的地方，可以指定类，属性或者方法等，有较多选择</li>
<li>@Inherited 继承功能，当超类使用了这个注解，他的子类也会使用上这个注解。</li>
<li>@Repeatable 可重复</li>
</ul>
<h4 id="三、动态代理"><a href="#三、动态代理" class="headerlink" title="三、动态代理"></a>三、动态代理</h4><ul>
<li>代理模式，中间人模式，常见的场景是用户要做一件事情，不会自己亲自做，而是会让中介去做，帮自己实现，面向对象程序设计中很常见的设计模式。代理流程如下：<br><img src="https://s10.mogucdn.com/mlcdn/c45406/180910_09aggbed258jhcd6jac67350166f1_1542x324.jpg" alt=""></li>
<li>动态代理可以用来做方法的功能增强，对代码无侵入，动态代理使用Proxy的静态方法newProxyInstance动态创建代理，如下</li>
</ul>
<figure class="highlight delphi"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">Object</span> newProxyInstance(ClassLoader loader,<span class="comment">//类加载器</span></span><br><span class="line"> <span class="keyword">Class</span><?>[] interfaces, <span class="comment">//代理接口</span></span><br><span class="line"> InvocationHandler h)<span class="comment">//关联接口</span></span><br></pre></td></tr></table></figure>
<ul>
<li>要创建动态代理，核心是要实现InvocationHandler接口和invoke方法，比如，要为一个接口的功能实现进行日志打印，相关流程:</li>
</ul>
<figure class="highlight cs"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//动态代理只能为接口创建代理</span></span><br><span class="line"><span class="keyword">interface</span> <span class="title">Work</span>{</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">getInfo</span>(<span class="params"></span>)</span>;</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">doWork</span>(<span class="params"></span>)</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">HomeWork</span> <span class="keyword">implements</span> <span class="title">Work</span></span>{</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getInfo</span><span class="params">()</span></span>{</span><br><span class="line"> System.out.println(<span class="string">"收集资料"</span>);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">doWork</span><span class="params">()</span></span>{</span><br><span class="line"> System.out.println(<span class="string">"正式工作"</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<figure class="highlight cs"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"> <span class="comment">//增强功能</span></span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">class</span> <span class="title">WorkLog</span> {</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">log</span>(<span class="params"></span>)</span>{</span><br><span class="line"> System.<span class="keyword">out</span>.println(<span class="string">"工作记录......"</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<figure class="highlight aspectj"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> java.lang.reflect.InvocationHandler;</span><br><span class="line"><span class="keyword">import</span> java.lang.reflect.Method;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">WorkInvocationHandler</span> <span class="keyword">implements</span> <span class="title">InvocationHandler</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> Object <span class="keyword">target</span>;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> <span class="function"><span class="keyword">void</span> <span class="title">setTarget</span><span class="params">(Object <span class="keyword">target</span>)</span></span>{</span><br><span class="line"> <span class="keyword">this</span>.<span class="keyword">target</span> = <span class="keyword">target</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//注意抛出异常，实现invoke方法</span></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="keyword">public</span> <span class="function">Object <span class="title">invoke</span><span class="params">(Object proxy, Method method, Object[] args)</span> <span class="keyword">throws</span> Throwable</span>{</span><br><span class="line"> WorkLog workLog = <span class="keyword">new</span> WorkLog();</span><br><span class="line"> workLog.log();</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">return</span> method.<span class="title">invoke</span><span class="params">(<span class="keyword">target</span>, args)</span></span>;</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<figure class="highlight aspectj"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"> <span class="keyword">import</span> java.lang.reflect.Proxy;</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">MyProxyFactory</span></span>{</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="function">Object <span class="title">getProxy</span><span class="params">(Object <span class="keyword">target</span>)</span> <span class="keyword">throws</span> Exception</span>{</span><br><span class="line"> <span class="comment">// 实例化对象</span></span><br><span class="line"> WorkInvocationHandler <span class="keyword">handler</span> = <span class="keyword">new</span> WorkInvocationHandler();</span><br><span class="line"> <span class="keyword">handler</span>.setTarget(<span class="keyword">target</span>);</span><br><span class="line"> <span class="keyword">return</span> Proxy.newProxyInstance(<span class="keyword">target</span>.getClass().getClassLoader(),</span><br><span class="line"> <span class="keyword">target</span>.getClass().getInterfaces(),<span class="keyword">handler</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<figure class="highlight aspectj"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="function"><span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>{</span><br><span class="line"> <span class="comment">// 实例化一个被代理对象</span></span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> Work <span class="keyword">target</span> = <span class="keyword">new</span> HomeWork();</span><br><span class="line"> Work work = (Work) MyProxyFactory.getProxy(<span class="keyword">target</span>);</span><br><span class="line"> work.getInfo();</span><br><span class="line"> work.doWork();</span><br><span class="line"> }<span class="keyword">catch</span> (Exception ignored){}</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><img src="https://s10.mogucdn.com/mlcdn/c45406/180910_13cb2i6a3el5a98e0i1ec0jh0e141_1102x342.jpg" alt=""></p>
<h4 id="四、类加载机制"><a href="#四、类加载机制" class="headerlink" title="四、类加载机制"></a>四、类加载机制</h4><h5 id="1、概述"><a href="#1、概述" class="headerlink" title="1、概述"></a>1、概述</h5><ul>
<li>Java代码需要运行，首先需要将源代码进行编译生成 .class 文件，然后 JVM 加载 .class 字节码文件到内存，而 .class 文件是怎样被加载到 JVM 中的就是Java 类加载</li>
</ul>
<h5 id="2、分类"><a href="#2、分类" class="headerlink" title="2、分类"></a>2、分类</h5><ul>
<li>AppClassLoader 应用加载器，也称为系统加载器，会加载来自CLASSPATH中的类和包，默认情况下，其它类加载器会将它作为父类加载器</li>
<li>ExtClassloader 拓展类加载器，主要加载Java的拓展类库</li>
<li>BootStrapClassLoader 启动类加载器，是最顶层的父类加载器，主要用来加载java的核心类</li>
</ul>
<h5 id="3、加载过程"><a href="#3、加载过程" class="headerlink" title="3、加载过程"></a>3、加载过程</h5><ul>
<li>加载流程如下：<br><img src="https://s10.mogucdn.com/mlcdn/c45406/180910_47ccclakc5d8d9g7k68bb4dkbl5b3_1296x400.jpg" alt=""><ul>
<li>加载过程采用双亲委派模型，当一个类加载器收到类加载任务时，会有限交给父类处理，父类无法完成时才会尝试自行加载任务。保证了使用不同的类加载器最终得到的都是同一个对象。</li>
</ul>
</li>
</ul>
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<h1 id="多线程"><a href="#多线程" class="headerlink" title="多线程"></a>多线程</h1><h3 id="一、概念"><a href="#一、概念" class="headerlink" title="一、概念"></a>一、概念</h3><h4 id="1、进程和线程的概念"><a href="#1、进程和线程的概念" class="headerlink" title="1、进程和线程的概念"></a>1、进程和线程的概念</h4><ul>
<li>进程和线程都是操作系统中的概念，操作系统对进程和线程的严格定义是：进程是具有一定独立功能的程序，是系统进行资源分配和调度的独立单位。线程是进程的实体，是cpu调度和分配的基本单位。</li>
</ul>
<h4 id="2、进程与线程的关系"><a href="#2、进程与线程的关系" class="headerlink" title="2、进程与线程的关系"></a>2、进程与线程的关系</h4><ul>
<li>一个线程只能属于一个进程，而一个进程可以有多个线程。 </li>
<li>同一进程的所有线程共享该进程的资源。 </li>
<li>线程在执行过程中，不同进程的线程间要利用消息通信的办法实现数据同步。 </li>
</ul>
<h4 id="3、线程的生命周期"><a href="#3、线程的生命周期" class="headerlink" title="3、线程的生命周期"></a>3、线程的生命周期</h4><ul>
<li>主要有创建，就绪，运行，阻塞，销毁几个状态，如图：</li>
</ul>
<p><img src="https://s10.mogucdn.com/mlcdn/c45406/180910_3c2dik9ehd52bc7hg4d10da13e7jb_1096x446.jpg" alt=""></p>
<h4 id="2、java与多线程"><a href="#2、java与多线程" class="headerlink" title="2、java与多线程"></a>2、java与多线程</h4><ul>
<li>java为了提升程序性能，也引入了多线程概念，通过多线程，在一些场景能极大提升性能，实现线程主要有两种方式，一种继承Thread类，另一种实现Runable接口，<h5 id="2-1-继承Thread类型"><a href="#2-1-继承Thread类型" class="headerlink" title="2.1 继承Thread类型"></a>2.1 继承Thread类型</h5></li>
<li>创建线程，可以通过继承Thread类并实现run()方法的形式，run()里面编写实际要运行的代码，运行时通过start（）方法将线程设为可运行态，并不是直接执行，具体调用还是要操作系统决定。</li>
</ul>
<figure class="highlight scala"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 继承Thread</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line">public <span class="class"><span class="keyword">class</span> <span class="title">TestThread</span> <span class="keyword">extends</span> <span class="title">Thread</span></span>{</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> <span class="type">String</span> threadName;</span><br><span class="line"></span><br><span class="line"> public <span class="type">TestThread</span>(<span class="type">String</span> name){</span><br><span class="line"> <span class="keyword">this</span>.threadName=name;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> public void run(){</span><br><span class="line"> <span class="type">System</span>.out.print(threadName);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="2-2-实现Runnable接口"><a href="#2-2-实现Runnable接口" class="headerlink" title="2.2 实现Runnable接口"></a>2.2 实现Runnable接口</h5><ul>
<li>线程类通过实现Runnable接口，实现run()方法，也能实现线程调用，和继承Thread类类似，如下：</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">RunnableThread</span> <span class="keyword">implements</span> <span class="title">Runnable</span></span>{</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> String threadName;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="title">RunnableThread</span><span class="params">(String name)</span></span>{</span><br><span class="line"> <span class="keyword">this</span>.threadName=name;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">run</span><span class="params">()</span></span>{</span><br><span class="line"> System.out.println(threadName);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="2-3-详细的启动过程"><a href="#2-3-详细的启动过程" class="headerlink" title="2.3 详细的启动过程"></a>2.3 详细的启动过程</h5><ul>
<li>1、通过new创建一个线程对象</li>
<li>2、调用线程对象的start()方法，使线程处理Runnable可运行状态，等待调用</li>
<li>3、当被调用时，执行run()中的代码</li>
<li>4、当线程因为原因在运行时放弃cpu调用时(比如被优先级高的线程抢占)，便会进入阻塞状态，当要继续运行时，需要重新进入可运行状态。</li>
<li>5、执行完成，会进入销毁状态。</li>
</ul>
<h4 id="3、线程同步"><a href="#3、线程同步" class="headerlink" title="3、线程同步"></a>3、线程同步</h4><ul>
<li>同一个进程的线程资源是共享的，当操作共享资源时，会存在问题，为了避免临界区造成的问题，线程之间需要进行同步，主要有下面几种同步方式</li>
</ul>
<h5 id="3-1、使用synchronized进行修饰"><a href="#3-1、使用synchronized进行修饰" class="headerlink" title="3.1、使用synchronized进行修饰"></a>3.1、使用synchronized进行修饰</h5><ul>
<li>在需要同步的方法面前加入synchronized进行修饰，synchronized会将对象锁住，能够保证在同一时刻只有一个线程访问，在调用方法之前，需要先获得内置锁，同时，除了修饰方法，还能修饰代码块</li>
</ul>
<figure class="highlight aspectj"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="function"><span class="keyword">synchronized</span> <span class="title">saveMoney</span><span class="params">()</span></span>{<span class="comment">//todo somethind};</span></span><br></pre></td></tr></table></figure>
<figure class="highlight scala"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">synchronized(<span class="class"><span class="keyword">object</span>)</span>{}; <span class="comment">//修饰对象</span></span><br></pre></td></tr></table></figure>
<h5 id="3-2、使用Lock锁"><a href="#3-2、使用Lock锁" class="headerlink" title="3.2、使用Lock锁"></a>3.2、使用Lock锁</h5><ul>
<li>锁机制也能保证同一个时刻只能有一个线程进行访问,在在java.util.concurrent.locks包中有很多Lock的实现类，常用的有ReentrantLock可重入锁等</li>
</ul>
<figure class="highlight cs"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"> Lock l = ...; <span class="comment">//lock实现对象对象</span></span><br><span class="line">l.<span class="keyword">lock</span>();</span><br><span class="line"><span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//todo something</span></span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> l.unlock();</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="3-3-volatile"><a href="#3-3-volatile" class="headerlink" title="3.3 volatile"></a>3.3 volatile</h5><ul>
<li>volatile主要保证了一个共享变量在多个线程访问的情况下，保证了共享变量的可见性，比如一个线程对变量进行了修改，另一个线程能同步到修改的值。</li>
</ul>
<h4 id="4、线程池"><a href="#4、线程池" class="headerlink" title="4、线程池"></a>4、线程池</h4><ul>
<li>在单个线程的使用中，频繁的创建销毁线程对象损耗较多的时间，影响系统性能，当有任务来时，临时创建性能也非常低效，节省了时间和效率。所以在多线程的开发中，尽量使用线程池的形式。</li>
</ul>
<h5 id="4-1、ThreadPoolExecutor"><a href="#4-1、ThreadPoolExecutor" class="headerlink" title="4.1、ThreadPoolExecutor"></a>4.1、ThreadPoolExecutor</h5><ul>
<li>使用ThreadPoolExecutor进行创建线程池,用法</li>
</ul>
<figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="title">ThreadPoolExecutor</span><span class="params">(<span class="keyword">int</span> corePoolSize,</span></span></span><br><span class="line"><span class="function"><span class="params"> <span class="keyword">int</span> maximumPoolSize,</span></span></span><br><span class="line"><span class="function"><span class="params"> <span class="keyword">long</span> keepAliveTime,</span></span></span><br><span class="line"><span class="function"><span class="params"> TimeUnit unit,</span></span></span><br><span class="line"><span class="function"><span class="params"> BlockingQueue<Runnable> workQueue)</span> </span>{</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<ul>
<li>corePoolSize是核心池的大小，maximumPoolSize最大线程数，keepAliveTime当没有任务时线程的存活时间，weekQueue阻塞队列，用来保存执行的任务，unit时间单位</li>
<li>协作流程：线程优先向 CorePool 中提交；在 Corepool 满了之后，线程被提交到任务队列，等待线程池空闲；在任务队列满了之后 corePool 还没有空闲，那么任务将被提交到 maxPool 中，如果 MaxPool 满了之后执行 task 拒绝策略。</li>
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<h1 id="Java集合框架"><a href="#Java集合框架" class="headerlink" title="Java集合框架"></a>Java集合框架</h1><h2 id="1、概述"><a href="#1、概述" class="headerlink" title="1、概述"></a>1、概述</h2><ul>
<li>java除了提供基本的数据类型支持外，还提供了对数据对象类型的存储框架，可以非常高效的，方便的操纵这些数据对象，并且能动态增长，集合可以用来存储、检索、操作、通信，它主要包含接口和实现类一些具体的操作方法。</li>
<li>java的集合框架主要有两种，一种是集合（Collection）,集合是存储一类元素的结合，它是最基本的容器接口，继承了Iterable接口。另一种是图，它存储了键值对的映射关系，通过键能得到值。</li>
</ul>
<h2 id="2、Collection"><a href="#2、Collection" class="headerlink" title="2、Collection"></a>2、Collection</h2><ul>
<li>Collection接口有三种子类型，分别为List，Set和Queue，由抽象类到具体的实现类，常用的有<h4 id="1、List介绍"><a href="#1、List介绍" class="headerlink" title="1、List介绍"></a>1、List介绍</h4></li>
<li>List容器中的元素是有序可重复的，它能够控制每个元素的插入位置，用户还可以直接通过索引来进行访问。List的实现类还有LindedList,ArrayList,vector和stack.<h4 id="2、Set介绍"><a href="#2、Set介绍" class="headerlink" title="2、Set介绍"></a>2、Set介绍</h4></li>
<li>Set里面存储的元素都是不重复的，并且里面的元素是无序的</li>
</ul>
<h4 id="3、Queue介绍"><a href="#3、Queue介绍" class="headerlink" title="3、Queue介绍"></a>3、Queue介绍</h4><ul>
<li>队列继承了Collection接口，和List,Set是同一个级别的，只允许在一端进行插入操作，另一端进行删除操作。具有先进先出的特性</li>
</ul>
<h4 id="4、Map"><a href="#4、Map" class="headerlink" title="4、Map"></a>4、Map</h4><ul>
<li>在程序中用于管理映射关系</li>
<li>map里面的key和value是一一对应的，并且不允许里面的key重复</li>
<li>map里面最重要的有一个entry方法，里面定义了对key或者value的获取方法</li>
</ul>
<h5 id="4-1-HashMap"><a href="#4-1-HashMap" class="headerlink" title="4.1 HashMap"></a>4.1 HashMap</h5><ul>
<li>HashMap是最常用的map，存储根据键的hashCode来进行存储，根据键可以直接获取值，访问速度很快。</li>
<li>遍历方式：遍历方式有根据keySet()值遍历和entrySet()键值进行遍历，还有迭代器iterator()的遍历方式。</li>
<li>iterator（）方法的遍历：</li>
</ul>
<figure class="highlight armasm"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"># 使用keySet进行遍历</span><br><span class="line"><span class="keyword">Iterator<String> </span><span class="keyword">iterator </span>= <span class="meta">map</span>.keySet().<span class="keyword">iterator();</span></span><br><span class="line"><span class="keyword">while </span>(<span class="keyword">iterator.hasNext()) </span>{</span><br><span class="line"> <span class="keyword">String </span>key = <span class="keyword">iterator.next();</span></span><br><span class="line"><span class="keyword"> </span> System.out.println(<span class="meta">map</span>.get(key))<span class="comment">;</span></span><br><span class="line">}</span><br><span class="line"># 使用entrySet()进行遍历</span><br><span class="line"><span class="keyword">Iterator<Map.Entry<String, </span><span class="keyword">String>> </span><span class="keyword">iterator </span>= <span class="meta">map</span>.entrySet().<span class="keyword">iterator();</span></span><br><span class="line"><span class="keyword">while </span>(<span class="keyword">iterator.hasNext()) </span>{</span><br><span class="line"> <span class="meta">Map</span>.Entry<<span class="keyword">String, </span><span class="keyword">String> </span><span class="meta">entry</span> = <span class="keyword">iterator.next();</span></span><br><span class="line"><span class="keyword"> </span> System.out.println(<span class="meta">entry</span>.getValue())<span class="comment">;</span></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h2 id="3、Iterator"><a href="#3、Iterator" class="headerlink" title="3、Iterator"></a>3、Iterator</h2><ul>
<li>iterator其实就是遍历，提供的标准化遍历容器内所有对象的方法，在迭代过程中，使用者不需要了解集合的内部的结构。</li>
<li>iterator主要有3个方法</li>
</ul>
<figure class="highlight stylus"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="title">hasNext</span><span class="params">()</span></span> <span class="comment">//判断是否还有元素供迭代</span></span><br><span class="line"><span class="function"><span class="title">next</span><span class="params">()</span></span> <span class="comment">//返回迭代的下一个元素</span></span><br><span class="line">remove（） <span class="comment">//移除迭代器返回的最后一个元素</span></span><br></pre></td></tr></table></figure>
<h2 id="4、泛型"><a href="#4、泛型" class="headerlink" title="4、泛型"></a>4、泛型</h2><ul>
<li>泛型主要是为了解决代码被不同对象的类型重用的问题，在集合框架中有广泛的使用。</li>
</ul>
<h4 id="4-1-泛型类"><a href="#4-1-泛型类" class="headerlink" title="4.1 泛型类"></a>4.1 泛型类</h4><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Pair</span><K, V> {</span></span><br><span class="line"> <span class="keyword">private</span> K key;</span><br><span class="line"> <span class="keyword">private</span> V value;</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<h4 id="4-2-泛型方法"><a href="#4-2-泛型方法" class="headerlink" title="4.2 泛型方法"></a>4.2 泛型方法</h4><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"> <span class="keyword">public</span> Class A{</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <T><span class="function">T <span class="title">test</span><span class="params">(T t)</span></span>{</span><br><span class="line"> <span class="keyword">return</span> t;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <T> <span class="function"><span class="keyword">void</span> <span class="title">hi</span><span class="params">(T t)</span></span>{</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h4 id="4-3-类型限定"><a href="#4-3-类型限定" class="headerlink" title="4.3 类型限定"></a>4.3 类型限定</h4><ul>
<li>需要限制类型时使用 extends</li>
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Python函数式编程
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<h3 id="1、Haskell到python函数式编程"><a href="#1、Haskell到python函数式编程" class="headerlink" title="1、Haskell到python函数式编程"></a>1、Haskell到python函数式编程</h3><p> 在学习python的过程中，一直体会着它的简洁和优雅，也钟情于它的简洁和优雅。但在一次偶然的机会中，在微博上看到某位博主贴出的一串Haskell代码，代码的透明，凝练，模块化，由小到大把我深深的吸引住，了解之余，发现Haskell是一门函数式编程语言，函数式编程语言有着深厚的数学知识作为基础，将电脑的运算看作是数学上的函数计算，可能这也是“数学之美”吧，在震惊之余，我也尝试了解，python是不是也支持函数式编程呢？结果是肯定的，Python作为一门命令式语言，但是也具备了函数式编程的特点。<br> 经过查询资料，不断学习，也慢慢的发现，函数式编程的确是很深奥，甚至于是一种晦涩难懂的编程模式，它将计算机中的运算看作是数学中函数的运算。掌握了可以让我们受益匪浅,也能体会到python一行代码实现强大功能的乐趣。</p>
<h3 id="2、函数式编程里的数学知识"><a href="#2、函数式编程里的数学知识" class="headerlink" title="2、函数式编程里的数学知识"></a>2、函数式编程里的数学知识</h3><p> 函数式编程里面含有很多的数学知识，函数作为函数式编程里面的一等公民，它来源于数学里面函数，而数学中，递归，合成与柯里化，高级函数。这些函数的转化关系，也都体现在了函数式编程中。</p>
<h3 id="3、函数式编程的特点"><a href="#3、函数式编程的特点" class="headerlink" title="3、函数式编程的特点"></a>3、函数式编程的特点</h3><ul>
<li>函数就是数据，函数是一等公民</li>
<li>纯函数:给一个值，一定返回另一个值，运算过程中部会被外部改变，具有透明性</li>
<li>无状态，区别于命令式编程</li>
<li>强编译器的支持（python不支持)</li>
<li></li>
</ul>
<h3 id="4、python函数式编程的实现"><a href="#4、python函数式编程的实现" class="headerlink" title="4、python函数式编程的实现"></a>4、python函数式编程的实现</h3><blockquote>
<p>python里面，函数式编程主要通过一些高阶函数来体现，所谓高阶函数，就是可以接受其他函数作为参数的函数。</p>
</blockquote>
<h4 id="1、内置函数的实现"><a href="#1、内置函数的实现" class="headerlink" title="1、内置函数的实现"></a>1、内置函数的实现</h4><ul>
<li><p>lambda 匿名函数</p>
<p>lambda 在很多编程语言中都有出现，作为一个匿名函数，可以不用让我们不必花时间编写那些简单的函数，比如：</p>
<figure class="highlight llvm"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">l = map(lambda <span class="keyword">x</span>: <span class="keyword">x</span>*<span class="keyword">x</span>, xrange(<span class="number">1</span>, <span class="number">10</span>)) # 对序列的每个数进行平方操作</span><br></pre></td></tr></table></figure>
</li>
<li><p>map()</p>
<p> map()本身接收一个函数和一个序列作为参数，然后将传入的函数依次作用在序列中的每个元素中，使用map可以对元素进行高效的处理迭代。比如:</p>
<figure class="highlight ini"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="attr">char_list</span> = [<span class="string">'1'</span>, <span class="string">'2'</span>, <span class="string">'3'</span>]</span><br><span class="line"><span class="attr">num_list</span> = map(int, num_list)</span><br></pre></td></tr></table></figure>
</li>
<li><p>reduce()</p>
<p> reduce()接收一个函数(必须是二元操作函数)和一个序列作为参数，函数会作用于序列的元素，并且会把结果作用于下一个元素。比如：</p>
<figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">l = [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>]</span><br><span class="line"><span class="function"><span class="keyword">def</span> <span class="title">add_exp</span><span class="params">(x, y)</span></span><span class="symbol">:</span></span><br><span class="line"> <span class="keyword">return</span> x+y</span><br><span class="line"></span><br><span class="line">res = reduce(add_exp, l)</span><br></pre></td></tr></table></figure>
</li>
<li><p>groupby()</p>
<p> groupby()是itertools中的一个函数，它的作用是对一个序列进行聚合分组运算，接收一个函数和一个序列，函数作用于参数key</p>
<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">from</span> itertools <span class="keyword">import</span> groupby</span><br><span class="line"></span><br><span class="line">l = [<span class="number">-1</span>, <span class="number">2</span>, <span class="number">5</span>, <span class="number">7</span>, <span class="number">13</span>]</span><br><span class="line"><span class="function"><span class="keyword">def</span> <span class="title">check_num</span><span class="params">(h)</span>:</span></span><br><span class="line"> <span class="keyword">if</span> h><span class="number">10</span>:</span><br><span class="line"> <span class="keyword">return</span> <span class="string">'big'</span></span><br><span class="line"> <span class="keyword">elif</span> h<=<span class="number">10</span> <span class="keyword">and</span> h><span class="number">5</span>:</span><br><span class="line"> <span class="keyword">return</span> <span class="string">'middle'</span></span><br><span class="line"> <span class="keyword">else</span>:</span><br><span class="line"> <span class="keyword">return</span> <span class="string">'small'</span></span><br><span class="line"> res = groupby(l, key=check_num)</span><br></pre></td></tr></table></figure>
</li>
</ul>
<ul>
<li><p>filter()</p>
<p> filter()接收一个过滤函数和一个序列，对序列的每个元素，使用过滤函数对元素进行过滤,结果为除去过滤结果为True的元素</p>
<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">l = [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>]</span><br><span class="line"><span class="function"><span class="keyword">def</span> <span class="title">is_prime</span><span class="params">(x)</span>:</span></span><br><span class="line"> <span class="keyword">if</span> x % <span class="number">2</span> == <span class="number">0</span>:</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">True</span></span><br><span class="line">res = filter(is_prime, l)</span><br></pre></td></tr></table></figure>
</li>
</ul>
<h4 id="2、语法的的实现"><a href="#2、语法的的实现" class="headerlink" title="2、语法的的实现"></a>2、语法的的实现</h4><ul>
<li><p>列表生成式</p>
<p> 列表生成式是python一个非常强大的魔法，使用它可以用一行代码表达很多语义，比如：</p>
<figure class="highlight applescript"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">[ x*x <span class="keyword">for</span> x <span class="keyword">in</span> xrange(<span class="number">10</span>) <span class="keyword">if</span> x % <span class="number">2</span> ==<span class="number">0</span>] <span class="comment"># 求10以内偶数的平方</span></span><br></pre></td></tr></table></figure>
</li>
<li><p>生成器generator</p>
<p> 生成器可以快速生成一个可迭代的对象，操作速度快。</p>
<figure class="highlight autoit"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">g_object = (x*x <span class="keyword">for</span> x <span class="keyword">in</span> xrange(<span class="number">5</span>)) <span class="meta"># xragne本身也是生成器</span></span><br><span class="line">g_object.<span class="keyword">next</span>() <span class="meta"># 使用next方法访问</span></span><br></pre></td></tr></table></figure>
</li>
</ul>
<h4 id="3、第三方模块的的实现"><a href="#3、第三方模块的的实现" class="headerlink" title="3、第三方模块的的实现"></a>3、第三方模块的的实现</h4><ul>
<li><p><a href="https://github.com/tobgu/pyrsistent" target="_blank" rel="noopener">pyrsistent</a> 构建纯函数</p>
<pre><code>pysistent第三方库实现了python中一些不可变的数据类型，对于函数而言，使用不可变的数据类型，更加方便我们构造出纯函数
</code></pre></li>
<li><p>functools partial 偏函数</p>
<p> partial的作用可以通过参数调用绑定的函数，设置默认的参数值 </p>
</li>
<li><p>compose (高阶函数） </p>
<p> 当看到compose时， 我的第一反应是这不是和Redux框架中连接中间件的compose一样吗，事实也是这样，他们功能类型，通过compose，可以让函数绑定多个顺序函数。</p>
</li>
<li><p>toolz.functoolz curry</p>
<p> 用于实现函数柯里化，也就是多个单参数函数实现多参数函数的方法</p>
</li>
<li><p>fn模块 fn模块包含大量的易于构建函数式的语法糖</p>
</li>
<li>递归优化（注意Python递归1000个调用限制）</li>
</ul>
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