Merge pull request #119 from guy120494/fix-connection

Fix connection

README.md

@@ -229,7 +229,20 @@ Relay [specification for mutations](https://facebook.github.io/relay/graphql/mut
 
 ### Connection
 
-You can use `@GraphQLConnection` annotation to make a field iterable in adherence to Relay [Connection specification](https://facebook.github.io/relay/graphql/connections.htm).
+You can use `@GraphQLConnection` annotation to make a field iterable in adherence to Relay [Connection specification](https://facebook.github.io/relay/graphql/connections.htm).\
+If a field is annotated with the annotation, the associated dataFetcher must return an instance of `PaginatedData`.\
+The `PaginatedData` class holds the result of the connection:
+1. The data of the page
+2. Whether or not there is a next page and a previous page
+3. A method that returns for each entity the encoded cursor of the entity (it returns string)
+
+For you convenience, there is `AbstractPaginatedData` that can be extended.
+
+If you want to use you own implementation of connection, that's fine, just give a value to connection().\
+Please note that if you do so, you also have to specify your own connection validator that implements `ConnectionValidator`\
+(and should throw `@GraphQLConnectionException` if something is wrong) 
+
+NOTE: because `PropertyDataFetcher` and `FieldDataFetcher` can't handle connection, this annotation cant be used on a field that doesn't have a dataFetcher
 
 ### Customizing Relay schema
 

build.gradle

@@ -44,7 +44,6 @@ idea {
         vcs = 'Git'
     }
 }
-
 release {
     tagTemplate = 'v${version}'
     failOnPublishNeeded = false
@@ -152,12 +151,12 @@ bintray {
         vcsUrl = 'https://github.com/graphql-java/graphql-java-annotations'
         version {
             name = project.version
-            released  = new Date()
+            released = new Date()
         }
     }
 }
 
 task bundle(type: Bundle) {
-  from sourceSets.main.output
-  bndfile = file('bundle.bnd')
+    from sourceSets.main.output
+    bndfile = file('bundle.bnd')
 }

src/main/java/graphql/annotations/connection/AbstractPaginatedData.java

@@ -0,0 +1,45 @@
+/**
+ * Copyright 2016 Yurii Rashkovskii
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ */
+package graphql.annotations.connection;
+
+import java.util.Iterator;
+
+public abstract class AbstractPaginatedData<T> implements PaginatedData<T> {
+
+     boolean hasPreviousPage;
+     boolean hasNextPage;
+     Iterable<T> data;
+
+    public AbstractPaginatedData(boolean hasPreviousPage, boolean hasNextPage, Iterable<T> data) {
+        this.hasNextPage = hasNextPage;
+        this.hasPreviousPage = hasPreviousPage;
+        this.data = data;
+    }
+
+    @Override
+    public boolean hasNextPage() {
+        return hasNextPage;
+    }
+
+    @Override
+    public boolean hasPreviousPage() {
+        return hasPreviousPage;
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+        return data.iterator();
+    }
+}

src/main/java/graphql/annotations/connection/ConnectionDataFetcher.java

@@ -0,0 +1,52 @@
+/**
+ * Copyright 2016 Yurii Rashkovskii
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ */
+package graphql.annotations.connection;
+
+import graphql.relay.Connection;
+import graphql.schema.DataFetcher;
+import graphql.schema.DataFetchingEnvironment;
+
+import java.lang.reflect.Constructor;
+import java.util.Arrays;
+import java.util.Optional;
+
+import static graphql.annotations.processor.util.ReflectionKit.constructNewInstance;
+
+
+public class ConnectionDataFetcher<T> implements DataFetcher<Connection<T>> {
+    private final DataFetcher<?> actualDataFetcher;
+    private final Constructor<ConnectionFetcher<T>> constructor;
+
+    @SuppressWarnings("unchecked")
+    public ConnectionDataFetcher(Class<? extends ConnectionFetcher<T>> connection, DataFetcher<?> actualDataFetcher) {
+        this.actualDataFetcher =  actualDataFetcher;
+        Optional<Constructor<ConnectionFetcher<T>>> constructor =
+                Arrays.stream(connection.getConstructors()).
+                        filter(c -> c.getParameterCount() == 1).
+                        map(c -> (Constructor<ConnectionFetcher<T>>) c).
+                        findFirst();
+        if (constructor.isPresent()) {
+            this.constructor = constructor.get();
+        } else {
+            throw new IllegalArgumentException(connection.getSimpleName() + " doesn't have a single argument constructor");
+        }
+    }
+
+    @Override
+    public Connection<T> get(DataFetchingEnvironment environment) {
+        ConnectionFetcher<T> conn = constructNewInstance(constructor, actualDataFetcher);
+        return conn.get(environment);
+    }
+}

src/main/java/graphql/annotations/connection/ConnectionFetcher.java

@@ -0,0 +1,21 @@
+/**
+ * Copyright 2016 Yurii Rashkovskii
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ */
+package graphql.annotations.connection;
+
+import graphql.relay.Connection;
+import graphql.schema.DataFetcher;
+
+public interface ConnectionFetcher<T> extends DataFetcher<Connection<T>> {
+}

src/main/java/graphql/annotations/connection/ConnectionValidator.java

@@ -0,0 +1,22 @@
+/**
+ * Copyright 2016 Yurii Rashkovskii
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ */
+package graphql.annotations.connection;
+
+import java.lang.reflect.AccessibleObject;
+
+public interface ConnectionValidator {
+
+    void validate(AccessibleObject field);
+}

src/main/java/graphql/annotations/annotationTypes/GraphQLConnection.java → src/main/java/graphql/annotations/connection/GraphQLConnection.java

@@ -12,10 +12,8 @@
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  */
-package graphql.annotations.annotationTypes;
+package graphql.annotations.connection;
 
-import graphql.annotations.dataFetchers.connection.Connection;
-import graphql.annotations.dataFetchers.connection.DispatchingConnection;
 
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
@@ -24,7 +22,7 @@
 
 /**
  * Specifies that the annotated field or method (given it is also
- * annotated with {@link GraphQLField}) is a collection that will
+ * annotated with {@link graphql.annotations.annotationTypes.GraphQLField}) is a collection that will
  * be adhering <a href="https://facebook.github.io/relay/graphql/connections.htm">Relay Connection specification</a>
  *
  * At the moment, the only allowed type for such field is <code>List&lt;?&gt;</code>
@@ -33,16 +31,25 @@
 @Retention(RetentionPolicy.RUNTIME)
 public @interface GraphQLConnection {
     /**
-     * By default, a simple List connection is specified, but can be overridden using
-     * this property to allow for more efficient fetching procedures (limiting database queries, etc.)
+     * By default, a paginated data connection is specified.
+     * this property allows for more efficient fetching procedures (limiting database queries, etc.)
+     * NOTE: if you override this, you should also override the validator field, and specify
+     * your own connection validator
      * @return a connection class
      */
-    Class<? extends Connection> connection() default DispatchingConnection.class;
+    Class<? extends ConnectionFetcher> connection() default PaginatedDataConnectionFetcher.class;
 
     /**
      * By default, wrapped type's name is used for naming TypeConnection, but can be overridden
      * using this property
      * @return the wrapped type's name
      */
     String name() default "";
+
+    /**
+     * By default, the the validator validates a paginated data connection.
+     * Can be overridden (and should be) if you are using a custom connection
+     * @return a connection validator
+     */
+    Class <? extends ConnectionValidator> validator() default PaginatedDataConnectionTypeValidator.class;
 }

src/main/java/graphql/annotations/connection/GraphQLConnectionException.java

@@ -0,0 +1,22 @@
+/**
+ * Copyright 2016 Yurii Rashkovskii
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ */
+package graphql.annotations.connection;
+
+class GraphQLConnectionException extends RuntimeException {
+
+    GraphQLConnectionException(String error) {
+        super(error);
+    }
+}

src/main/java/graphql/annotations/connection/PaginatedData.java

@@ -0,0 +1,48 @@
+/**
+ * Copyright 2016 Yurii Rashkovskii
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ */
+package graphql.annotations.connection;
+
+/**
+ * This class is the result of a connection. Every Graphql connection field must return this interface
+ * <p>
+ * NOTE: this interface extends Iterable. The data is retrieved from the "iterator" function.
+ * Please implement the iterator with data structure that has order
+ *
+ * @param <T> the data of which we paginated over
+ */
+public interface PaginatedData<T> extends Iterable<T> {
+
+    /**
+     * Whether or not this is the last page
+     *
+     * @return true if there is a next page, false otherwise
+     */
+    boolean hasNextPage();
+
+    /**
+     * Whether or not this is the first page
+     *
+     * @return true if there is a previous page, false otherwise
+     */
+    boolean hasPreviousPage();
+
+    /**
+     * get the encoded cursor of the entity
+     *
+     * @param entity the entity
+     * @return String representation of the cursor of the entity
+     */
+    String getCursor(T entity);
+}

src/main/java/graphql/annotations/connection/PaginatedDataConnectionFetcher.java

@@ -0,0 +1,74 @@
+/**
+ * Copyright 2016 Yurii Rashkovskii
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ */
+package graphql.annotations.connection;
+
+import graphql.relay.*;
+import graphql.schema.DataFetcher;
+import graphql.schema.DataFetchingEnvironment;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ * Use this class in {@link GraphQLConnection} to do a real pagination,
+ * i.e you fetch each time the relevant data, you make the cursors and
+ * you decide if there are previous or next pages
+ * <p>
+ * Note: If you are using the connection, the return type of the associated dataFetcher must implement {@link PaginatedData}
+ *
+ * @param <T> the entity type that is paginated
+ */
+public class PaginatedDataConnectionFetcher<T> implements ConnectionFetcher<T> {
+
+    private DataFetcher<PaginatedData<T>> paginationDataFetcher;
+
+    public PaginatedDataConnectionFetcher(DataFetcher<PaginatedData<T>> paginationDataFetcher) {
+        this.paginationDataFetcher = paginationDataFetcher;
+    }
+
+    @Override
+    public Connection<T> get(DataFetchingEnvironment environment) {
+        PaginatedData<T> paginatedData = paginationDataFetcher.get(environment);
+        if (paginatedData == null) {
+            return new DefaultConnection<>(Collections.emptyList(), new DefaultPageInfo(null,null,false,false));
+        }
+        List<Edge<T>> edges = buildEdges(paginatedData);
+        PageInfo pageInfo = getPageInfo(edges, paginatedData);
+        return new DefaultConnection<>(edges, pageInfo);
+    }
+
+    private PageInfo getPageInfo(List<Edge<T>> edges, PaginatedData<T> paginatedData) {
+        ConnectionCursor firstCursor = edges.get(0).getCursor();
+        ConnectionCursor lastCursor = edges.get(edges.size() - 1).getCursor();
+        return new DefaultPageInfo(
+                firstCursor,
+                lastCursor,
+                paginatedData.hasPreviousPage(),
+                paginatedData.hasNextPage()
+        );
+    }
+
+    private List<Edge<T>> buildEdges(PaginatedData<T> paginatedData) {
+        Iterator<T> data = paginatedData.iterator();
+        List<Edge<T>> edges = new ArrayList<>();
+        for (; data.hasNext(); ) {
+            T entity = data.next();
+            edges.add(new DefaultEdge<>(entity, new DefaultConnectionCursor(paginatedData.getCursor(entity))));
+        }
+        return edges;
+    }
+}