feat(examples): Introduce new Java 25 example

examples/httpserver-java25-base/.dockerignore

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+/Makefile.uk
+/.unikraft/
+/.config*

examples/httpserver-java25-base/.gitignore

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+/Makefile.uk
+/.unikraft/
+/.config*

examples/httpserver-java25-base/Dockerfile

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+FROM openjdk:25-rc-oraclelinux9 AS build
+
+ENV JAVA_HOME=/usr/java/openjdk-25
+
+RUN ldconfig $JAVA_HOME/lib/server/
+
+WORKDIR /src
+
+COPY ./SimpleHttpServer.java /src/SimpleHttpServer.java
+
+RUN javac SimpleHttpServer.java
+
+FROM alpine:3 AS sys
+
+FROM scratch
+
+COPY --from=build /usr/lib64/libc.so.6 /usr/lib64/
+COPY --from=build /usr/lib64/libstdc++.so.6 /usr/lib64/
+COPY --from=build /usr/lib64/libm.so.6 /usr/lib64/
+COPY --from=build /usr/lib64/libz.so.1 /usr/lib64/
+COPY --from=build /usr/lib64/libgcc_s.so.1 /usr/lib64/
+COPY --from=build /lib64/ld-linux-x86-64.so.2 /lib64/
+COPY --from=build /etc/ld.so.cache /etc/ld.so.cache
+
+COPY --from=build $JAVA_HOME/ /usr/lib/jvm/java-25-runtime/
+
+COPY --from=build /src/SimpleHttpServer.class /usr/src/SimpleHttpServer.class

examples/httpserver-java25-base/Kraftfile

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+spec: v0.6
+
+name: httpserver-java25-base
+
+rootfs: ./Dockerfile
+
+cmd: ["/usr/lib/jvm/java-25-runtime/bin/java", "-classpath", "/usr/src/", "SimpleHttpServer"]
+
+runtime: base:latest

examples/httpserver-java25-base/README.md

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+# Java 25 HTTP Server
+
+This directory contains the [Java](https://www.java.com/en/) runtime on Unikraft, in binary compatibility mode.
+It implements a simple HTTP server running on Unikraft that provides a simple response to each request.
+
+## Run and Use
+
+Use `kraft` to run the image and start a Unikraft instance:
+
+```bash
+kraft run --rm -M 1024M -p 8080:8080 --plat qemu --arch x86_64 .
+```
+
+If the `--plat` argument is left out, it defaults to `qemu`.
+If the `--arch` argument is left out, it defaults to your system's CPU architecture.
+
+Once executed, it will open port `8080` and wait for connections.
+To test it, you can use `curl`:
+
+```bash
+curl localhost:8080
+```
+
+You should see a "Hello, World!" message.
+
+## Inspect and Close
+
+To list information about the Unikraft instance, use:
+
+```bash
+kraft ps -a
+```
+
+```text
+NAME          KERNEL                      ARGS                               CREATED        STATUS   MEM    PORTS                   PLAT
+upbeat_jenny  project://httpserver-java25:qemu/x86_64  /usr/lib/jvm/java-25-runtime[...]  5 seconds ago  running  2048M  0.0.0.0:8080->8080/tcp  qemu/x86_64
+```
+
+The instance name is `upbeat_jenny`.
+To close the Unikraft instance, use:
+
+```bash
+kraft rm upbeat_jenny
+```
+
+Note that closing the `kraft run` command (e.g., via `Ctrl+c`) does not kill the Unikraft instance.
+If you want the Unikraft instance closed when closing the `kraft run` command, use the `--rm` option:
+
+```bash
+kraft run --rm -M 1024M -p 8080:8080 --plat qemu --arch x86_64 .
+```
+
+## Build and Run Locally
+
+The commands so far used the pre-build Java image available in the Unikraft registry.
+
+In oder to to build a local Java image, clone this repository and `cd` into this directory.
+Then use `kraft` to build an image locally:
+
+```bash
+kraft build --no-cache --no-update --plat qemu --arch x86_64
+```
+
+Similar to the `kraft run` command, if the `--plat` argument is left out, it defaults to `qemu`.
+If the `--arch` argument is left out, it defaults to your system's CPU architecture.
+
+In order to run the locally built image, use `.` (_dot_, the current directory)  as the final argument to the `kraft run` command:
+
+```bash
+kraft run --rm -M 1024M -p 8080:8080 --plat qemu --arch x86_64 .
+```
+
+Same as above, it will open port `8080` and wait for connections.
+
+## `kraft` and `sudo`
+
+Mixing invocations of `kraft` and `sudo` can lead to unexpected behavior.
+Read more about how to start `kraft` without `sudo` at [https://unikraft.org/sudoless](https://unikraft.org/sudoless).
+
+## Learn More
+
+- [How to run unikernels locally](https://unikraft.org/docs/cli/running)
+- [How to build `Dockerfile` root filesystems with BuildKit](https://unikraft.org/docs/getting-started/integrations/buildkit)

examples/httpserver-java25-base/SimpleHttpServer.java

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+// https://www.logicbig.com/tutorials/core-java-tutorial/http-server/http-server-basic.html
+
+import com.sun.net.httpserver.HttpContext;
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpServer;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.net.InetSocketAddress;
+
+public class SimpleHttpServer {
+    private static final int listenPort = 8080;
+
+    public static void main(String[] args) throws IOException {
+        HttpServer server = HttpServer.create(new InetSocketAddress(listenPort), 0);
+        HttpContext context = server.createContext("/");
+        context.setHandler(SimpleHttpServer::handleRequest);
+        System.out.println("Waiting for HTTP connections on port " + listenPort + " ...");
+        server.start();
+    }
+
+    private static void handleRequest(HttpExchange exchange) throws IOException {
+        String response = "Hello, World!\n";
+        exchange.sendResponseHeaders(200, response.getBytes().length); // response code and length
+        OutputStream os = exchange.getResponseBody();
+        os.write(response.getBytes());
+        os.close();
+    }
+
+}

examples/httpserver-java25/.dockerignore

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+/Makefile.uk
+/.unikraft/
+/.config*

examples/httpserver-java25/.gitignore

@@ -0,0 +1,3 @@
+/Makefile.uk
+/.unikraft/
+/.config*

examples/httpserver-java25/Dockerfile

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+FROM openjdk:25-rc-oraclelinux9 AS build
+
+ENV JAVA_HOME=/usr/java/openjdk-25
+
+RUN ldconfig $JAVA_HOME/lib/server/
+
+WORKDIR /src
+
+COPY ./SimpleHttpServer.java /src/SimpleHttpServer.java
+
+RUN javac SimpleHttpServer.java
+
+FROM alpine:3 AS sys
+
+FROM scratch
+
+COPY --from=build /usr/lib64/libc.so.6 /usr/lib64/
+COPY --from=build /usr/lib64/libstdc++.so.6 /usr/lib64/
+COPY --from=build /usr/lib64/libm.so.6 /usr/lib64/
+COPY --from=build /usr/lib64/libz.so.1 /usr/lib64/
+COPY --from=build /usr/lib64/libgcc_s.so.1 /usr/lib64/
+COPY --from=build /lib64/ld-linux-x86-64.so.2 /lib64/
+COPY --from=build /etc/ld.so.cache /etc/ld.so.cache
+
+COPY --from=build $JAVA_HOME/ /usr/lib/jvm/java-25-runtime/
+
+COPY --from=build /src/SimpleHttpServer.class /usr/src/SimpleHttpServer.class

examples/httpserver-java25/Kraftfile

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+spec: v0.6
+
+name: httpserver-java25-base
+
+rootfs: ./Dockerfile
+
+cmd: ["/usr/lib/jvm/java-25-runtime/bin/java", "-classpath", "/usr/src/", "SimpleHttpServer"]
+
+runtime: java:25

examples/httpserver-java25/README.md

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+# Java 25 HTTP Server
+
+This directory contains the [Java](https://www.java.com/en/) runtime on Unikraft, in binary compatibility mode.
+It implements a simple HTTP server running on Unikraft that provides a simple response to each request.
+
+## Run and Use
+
+Use `kraft` to run the image and start a Unikraft instance:
+
+```bash
+kraft run --rm -M 1024M -p 8080:8080 --plat qemu --arch x86_64 .
+```
+
+If the `--plat` argument is left out, it defaults to `qemu`.
+If the `--arch` argument is left out, it defaults to your system's CPU architecture.
+
+Once executed, it will open port `8080` and wait for connections.
+To test it, you can use `curl`:
+
+```bash
+curl localhost:8080
+```
+
+You should see a "Hello, World!" message.
+
+## Inspect and Close
+
+To list information about the Unikraft instance, use:
+
+```bash
+kraft ps -a
+```
+
+```text
+NAME          KERNEL                      ARGS                               CREATED        STATUS   MEM    PORTS                   PLAT
+upbeat_jenny  project://httpserver-java25:qemu/x86_64  /usr/lib/jvm/java-25-runtime[...]  5 seconds ago  running  2048M  0.0.0.0:8080->8080/tcp  qemu/x86_64
+```
+
+The instance name is `upbeat_jenny`.
+To close the Unikraft instance, use:
+
+```bash
+kraft rm upbeat_jenny
+```
+
+Note that closing the `kraft run` command (e.g., via `Ctrl+c`) does not kill the Unikraft instance.
+If you want the Unikraft instance closed when closing the `kraft run` command, use the `--rm` option:
+
+```bash
+kraft run --rm -M 1024M -p 8080:8080 --plat qemu --arch x86_64 .
+```
+
+## Build and Run Locally
+
+The commands so far used the pre-build Java image available in the Unikraft registry.
+
+In oder to to build a local Java image, clone this repository and `cd` into this directory.
+Then use `kraft` to build an image locally:
+
+```bash
+kraft build --no-cache --no-update --plat qemu --arch x86_64
+```
+
+Similar to the `kraft run` command, if the `--plat` argument is left out, it defaults to `qemu`.
+If the `--arch` argument is left out, it defaults to your system's CPU architecture.
+
+In order to run the locally built image, use `.` (_dot_, the current directory)  as the final argument to the `kraft run` command:
+
+```bash
+kraft run --rm -M 1024M -p 8080:8080 --plat qemu --arch x86_64 .
+```
+
+Same as above, it will open port `8080` and wait for connections.
+
+## `kraft` and `sudo`
+
+Mixing invocations of `kraft` and `sudo` can lead to unexpected behavior.
+Read more about how to start `kraft` without `sudo` at [https://unikraft.org/sudoless](https://unikraft.org/sudoless).
+
+## Learn More
+
+- [How to run unikernels locally](https://unikraft.org/docs/cli/running)
+- [How to build `Dockerfile` root filesystems with BuildKit](https://unikraft.org/docs/getting-started/integrations/buildkit)

examples/httpserver-java25/SimpleHttpServer.java

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+// https://www.logicbig.com/tutorials/core-java-tutorial/http-server/http-server-basic.html
+
+import com.sun.net.httpserver.HttpContext;
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpServer;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.net.InetSocketAddress;
+
+public class SimpleHttpServer {
+    private static final int listenPort = 8080;
+
+    public static void main(String[] args) throws IOException {
+        HttpServer server = HttpServer.create(new InetSocketAddress(listenPort), 0);
+        HttpContext context = server.createContext("/");
+        context.setHandler(SimpleHttpServer::handleRequest);
+        System.out.println("Waiting for HTTP connections on port " + listenPort + " ...");
+        server.start();
+    }
+
+    private static void handleRequest(HttpExchange exchange) throws IOException {
+        String response = "Hello, World!\n";
+        exchange.sendResponseHeaders(200, response.getBytes().length); // response code and length
+        OutputStream os = exchange.getResponseBody();
+        os.write(response.getBytes());
+        os.close();
+    }
+
+}

library/java/25/.dockerignore

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+/Makefile.uk
+/.unikraft/
+/.config*

library/java/25/.gitignore

@@ -0,0 +1,3 @@
+/Makefile.uk
+/.unikraft/
+/.config*

library/java/25/Dockerfile

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+FROM openjdk:25-rc-oraclelinux9 AS build
+
+ENV JAVA_HOME=/usr/java/openjdk-25
+
+RUN ldconfig $JAVA_HOME/lib/server/
+
+WORKDIR /src
+
+COPY ./SimpleHttpServer.java /src/SimpleHttpServer.java
+
+RUN javac SimpleHttpServer.java
+
+FROM alpine:3 AS sys
+
+FROM scratch
+
+COPY --from=build /usr/lib64/libc.so.6 /usr/lib64/
+COPY --from=build /usr/lib64/libstdc++.so.6 /usr/lib64/
+COPY --from=build /usr/lib64/libm.so.6 /usr/lib64/
+COPY --from=build /usr/lib64/libz.so.1 /usr/lib64/
+COPY --from=build /usr/lib64/libgcc_s.so.1 /usr/lib64/
+COPY --from=build /lib64/ld-linux-x86-64.so.2 /lib64/
+COPY --from=build /etc/ld.so.cache /etc/ld.so.cache
+
+COPY --from=build $JAVA_HOME/ /usr/lib/jvm/java-25-runtime/
+
+COPY --from=build /src/SimpleHttpServer.class /usr/src/SimpleHttpServer.class