pagination changes.

pom.xml

@@ -80,11 +80,11 @@
             <version>${graphql.java}</version>
         </dependency>
 
-        <!--        <dependency>-->
-<!--            <groupId>com.graphql-java</groupId>-->
-<!--            <artifactId>graphql-java-extended-validation</artifactId>-->
-<!--            <version>${graphql.java}</version>-->
-<!--        </dependency>-->
+        <dependency>
+            <groupId>com.graphql-java</groupId>
+            <artifactId>graphql-java-extended-validation</artifactId>
+            <version>${graphql.java}</version>
+        </dependency>
 
         <!--		<dependency>-->
         <!--			<groupId>com.netflix.graphql.dgs</groupId>-->

src/main/java/com/sarya/graphql/service/application/port/in/CustomerResolver.java

@@ -5,24 +5,34 @@
 import com.netflix.graphql.dgs.InputArgument;
 import com.sarya.graphql.service.codegen.types.Customer;
 import com.sarya.graphql.service.codegen.types.PaginationInput;
+import com.sarya.graphql.service.util.pagination.CursorDecoder;
+import com.sarya.graphql.service.util.pagination.CursorEncoder;
+import com.sarya.graphql.service.util.pagination.GenericConnection;
 import graphql.relay.Connection;
-import graphql.relay.SimpleListConnection;
 import graphql.schema.DataFetchingEnvironment;
+
 import java.util.List;
 import java.util.UUID;
+import lombok.AllArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 
 @DgsComponent
 @Slf4j
+@AllArgsConstructor
 public class CustomerResolver {
+
+  private final CursorEncoder cursorEncoder;
+  private final CursorDecoder cursorDecoder;
+
   @DgsQuery
   Connection<Customer> fetchCustomers(
       DataFetchingEnvironment dfe,
       @InputArgument PaginationInput paginationInput
   ) {
     log.info("pagination Input: {}", paginationInput);
+    int offset = cursorDecoder.apply(paginationInput.getAfter(), 0);
     var customer = Customer.newBuilder().name("James").customerId(UUID.randomUUID())
         .email("[email protected]").build();
-    return new SimpleListConnection<>(List.of(customer)).get(dfe);
+    return new GenericConnection<>(cursorEncoder, List.of(customer), offset).get(dfe);
   }
 }

src/main/java/com/sarya/graphql/service/application/port/in/ProductResolver.java

@@ -6,7 +6,7 @@
 import com.netflix.graphql.dgs.InputArgument;
 import com.sarya.graphql.service.application.usecase.CreateProductUseCase;
 import com.sarya.graphql.service.application.usecase.FetchProductUseCase;
-import com.sarya.graphql.service.codegen.types.CreateProduct;
+import com.sarya.graphql.service.codegen.types.CreateProductInput;
 import com.sarya.graphql.service.codegen.types.Product;
 import com.sarya.graphql.service.codegen.types.ProductStatus;
 import com.sarya.graphql.service.codegen.types.ProductType;
@@ -34,7 +34,7 @@ public List<Product> fetchProducts() {
   }
 
   @DgsMutation
-  public boolean createProduct(@InputArgument CreateProduct input) {
+  public boolean createProduct(@InputArgument CreateProductInput input) {
     log.info("incoming message: {}", input);
     Product output = new Product();
     BeanUtils.copyProperties(input, output, Product.class);

src/main/java/com/sarya/graphql/service/util/pagination/CursorDecoder.java

@@ -0,0 +1,26 @@
+package com.sarya.graphql.service.util.pagination;
+
+import com.google.common.base.Strings;
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
+import java.util.function.BiFunction;
+import org.apache.tomcat.util.codec.binary.StringUtils;
+import org.springframework.stereotype.Component;
+
+@Component
+public class CursorDecoder implements BiFunction<String, Integer, Integer> {
+
+  @Override
+  public Integer apply(String cursor, Integer defaultValue) {
+    if (Strings.isNullOrEmpty(cursor)) {
+      return defaultValue;
+    }
+    var hash = Base64.getDecoder().decode(cursor.getBytes(StandardCharsets.UTF_8));
+    var cursorLiteral = StringUtils.newStringUtf8(hash);
+    try {
+      return (Integer.valueOf(cursorLiteral.substring(5)));
+    } catch (NumberFormatException nfe) {
+      throw new RuntimeException("unparsable cursor: {}" + cursor);
+    }
+  }
+}

src/main/java/com/sarya/graphql/service/util/pagination/CursorEncoder.java

@@ -0,0 +1,16 @@
+package com.sarya.graphql.service.util.pagination;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
+import java.util.function.Function;
+import org.springframework.stereotype.Component;
+
+@Component
+public class CursorEncoder implements Function<Integer, String> {
+
+  @Override
+  public String apply(Integer offset) {
+    byte[] bytes = ("prefix" + offset).getBytes(StandardCharsets.UTF_8);
+    return Base64.getEncoder().encodeToString(bytes);
+  }
+}

src/main/java/com/sarya/graphql/service/util/pagination/GenericConnection.java

@@ -0,0 +1,57 @@
+package com.sarya.graphql.service.util.pagination;
+
+import graphql.relay.Connection;
+import graphql.relay.DefaultConnection;
+import graphql.relay.DefaultConnectionCursor;
+import graphql.relay.DefaultEdge;
+import graphql.relay.DefaultPageInfo;
+import graphql.relay.Edge;
+import graphql.relay.PageInfo;
+import graphql.schema.DataFetcher;
+import graphql.schema.DataFetchingEnvironment;
+import java.util.ArrayList;
+import java.util.List;
+import lombok.AllArgsConstructor;
+
+@AllArgsConstructor
+public class GenericConnection<T> implements DataFetcher<Connection<T>> {
+
+  private final CursorEncoder cursorEncoder;
+
+  private final List<T> data;
+  private final int offset;
+
+  @Override
+  public Connection<T> get(DataFetchingEnvironment environment) {
+    List<Edge<T>> edges = buildEdges();
+
+    if (edges.size() == 0) {
+      return emptyConnection();
+    }
+
+    var firstEdge = edges.get(0);
+    var lastEdge = edges.get(edges.size() - 1);
+
+    return new DefaultConnection<>(
+        edges,
+        new GenericPageInfo(firstEdge.getCursor(), lastEdge.getCursor(), false, false, edges.size())
+    );
+  }
+
+  private Connection<T> emptyConnection() {
+    PageInfo pageInfo = new DefaultPageInfo(null, null, false, false);
+    return new DefaultConnection<>(List.of(), pageInfo);
+  }
+
+  private List<Edge<T>> buildEdges() {
+    List<Edge<T>> edges = new ArrayList<>();
+    int ix = 0;
+    for (T object : data) {
+      edges.add(
+          new DefaultEdge<>(object, new DefaultConnectionCursor(cursorEncoder.apply(offset + ix++)))
+      );
+    }
+    return edges;
+  }
+
+}

src/main/java/com/sarya/graphql/service/util/pagination/GenericPageInfo.java

@@ -0,0 +1,22 @@
+package com.sarya.graphql.service.util.pagination;
+
+import graphql.relay.ConnectionCursor;
+import graphql.relay.DefaultPageInfo;
+import lombok.ToString;
+
+@ToString
+public class GenericPageInfo extends DefaultPageInfo {
+
+  private final long totalCount;
+
+  public GenericPageInfo(
+      ConnectionCursor startCursor,
+      ConnectionCursor endCursor,
+      boolean hasPreviousPage,
+      boolean hasNextPage,
+      long totalCount
+  ) {
+    super(startCursor, endCursor, hasPreviousPage, hasNextPage);
+    this.totalCount = totalCount;
+  }
+}

src/main/resources/application.yml

@@ -4,6 +4,7 @@ spring:
   graphql:
     graphiql:
       enabled: true
+
     #    websocket:
     #      path: /graphql
     schema:
@@ -24,6 +25,7 @@ dgs:
   reload: true
   graphql:
     enable-entity-fetcher-custom-scalar-parsing: true
+    schema-wiring-validation-enabled: true
     spring:
       webmvc:
         asyncdispatch:

src/main/resources/schema/schema.graphqls

@@ -1,6 +1,14 @@
+directive @connection on OBJECT
+directive @Range(min: Int = 0, max: Int = 2147483647, message: String= "Invalid input value") on ARGUMENT_DEFINITION | INPUT_FIELD_DEFINITION
+directive @Size(min : Int = 0, max : Int = 2147483647, message : String = "graphql.validation.Size.message")
+on ARGUMENT_DEFINITION | INPUT_FIELD_DEFINITION
+directive @NotBlank(message : String = "graphql.validation.NotBlank.message") on ARGUMENT_DEFINITION | INPUT_FIELD_DEFINITION
+
 scalar Currency
 scalar UUID
 scalar BigDecimal
+
+
 scalar Long
 
 type Query {
@@ -9,11 +17,11 @@ type Query {
 }
 
 type Mutation {
-    createProduct(input: CreateProduct): Boolean
+    createProduct(input: CreateProductInput): Boolean
 }
 
-input CreateProduct {
-    name: String
+input CreateProductInput {
+    name: String @NotBlank
     productType: ProductType
     productStatus: ProductStatus
     active: Boolean
@@ -77,6 +85,6 @@ type CustomerEdge {
 }
 
 input PaginationInput {
-    first: Int = 10
+    first: Int = 10 @Range(min: 1, max: 1000)
     after: String
 }