BAEL-1027: Introduction to GraphQL - initial commit (eugenp#2515)

* spring beans DI examples

* fix-1: shortening examples

* List of Rules Engines in Java

* BAEL-812: Openl-Tablets example added

* BAEL-812: artifacts names changed

* BAEL-812: moving rule-engines examples to rule-engines folder

* BAEL-812: removing evaluation article files

* BAEL-812: folder renamed

* BAEL-812: folder renamed

* BAEL-812: pom.xml - parent added

* BAEL-1027: Introduction to GraphQL - initial commit

graphql/graphql-java/payload-examples/createUser.json

@@ -0,0 +1,8 @@
+{
+  "query": "mutation($name: String! $email: String! $age: String! ){ createUser ( name: $name email: $email age: $age) { id name email age } }",
+  "parameters": {
+    "name": "John",
+	"email": "[email protected]",
+    "age": 34
+  }
+}

graphql/graphql-java/payload-examples/deleteUser.json

@@ -0,0 +1,6 @@
+{
+  "query": "mutation($name: String! ){ deleteUser ( id: $id) { id name email age} }",
+  "parameters": {
+    "id": 2
+  }
+}

graphql/graphql-java/payload-examples/listUsers.json

@@ -0,0 +1,4 @@
+{
+  "query": "{ listUsers{ id name email age}}",
+  "parameters": {}
+}

graphql/graphql-java/payload-examples/retrieveUser.json

@@ -0,0 +1,6 @@
+{
+  "query": "query($id: String!){ retrieveUser ( id: $id) { id name email} }",
+  "parameters": {
+    "id": 1
+  }
+}

graphql/graphql-java/payload-examples/searchName.json

@@ -0,0 +1,6 @@
+{
+  "query": "query($id: String!){ searchName ( id: $id) { id name email} }",
+  "parameters": {
+    "id": 2
+  }
+}

graphql/graphql-java/payload-examples/updateUser.json

@@ -0,0 +1,9 @@
+{
+	"query": "mutation($id: String! $name: String! $email: String! $age: String! ){ updateUser ( id: $id name: $name email: $email age: $age) { id name email age} }",
+	"parameters": {
+		"id": 1,
+		"name":"John updated",
+		"email": "[email protected]",
+		"age": 50
+	}
+}

graphql/graphql-java/pom.xml

@@ -0,0 +1,29 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<groupId>com.baeldung.graphql</groupId>
+	<artifactId>graphql-java</artifactId>
+	<version>1.0</version>
+
+	<name>graphql-java</name>
+
+	<parent>
+		<groupId>com.baeldung</groupId>
+		<artifactId>parent-modules</artifactId>
+		<version>1.0.0-SNAPSHOT</version>
+	</parent>
+
+	<dependencies>
+		<dependency>
+			<groupId>com.graphql-java</groupId>
+			<artifactId>graphql-java-annotations</artifactId>
+			<version>3.0.3</version>
+		</dependency>
+		<dependency>
+			<groupId>io.ratpack</groupId>
+			<artifactId>ratpack-core</artifactId>
+			<version>1.4.6</version>
+		</dependency>
+	</dependencies>
+</project>

graphql/graphql-java/src/main/java/com/baeldung/graphql/Application.java

@@ -0,0 +1,17 @@
+package com.baeldung.graphql;
+
+import ratpack.server.RatpackServer;
+
+import com.baeldung.graphql.handler.UserHandler;
+
+public class Application {
+    public static void main(String[] args) throws Exception {
+        new Application();
+    }
+
+    private Application() throws Exception {
+        final RatpackServer server = RatpackServer.of(s -> s.handlers(chain -> chain.post("users", new UserHandler())));
+        server.start();
+    }
+
+}

graphql/graphql-java/src/main/java/com/baeldung/graphql/entity/User.java

@@ -0,0 +1,78 @@
+package com.baeldung.graphql.entity;
+
+import java.util.List;
+
+import com.baeldung.graphql.handler.UserHandler;
+import com.baeldung.graphql.utils.SchemaUtils;
+
+import graphql.annotations.GraphQLField;
+import graphql.annotations.GraphQLName;
+
+@GraphQLName(SchemaUtils.USER)
+public class User {
+
+    @GraphQLField
+    private Long id;
+    @GraphQLField
+    private String name;
+    @GraphQLField
+    private String email;
+    @GraphQLField
+    private Integer age;
+
+    public User(String name, String email, Integer age) {
+        this.id = genId();
+        this.name = name;
+        this.email = email;
+        this.age = age;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Integer getAge() {
+        return age;
+    }
+
+    public void setAge(Integer age) {
+        this.age = age;
+    }
+
+    public static Long genId() {
+        Long id = 1L;
+        try {
+            List<User> users =  new UserHandler().getUsers();
+            for (User user : users)
+                id = (user.getId() > id ? user.getId() : id) + 1;
+
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+        return id;
+    }
+
+    public String toString() {
+        return "[id=" + id + ", name=" + name + ", email="+email+ ", age="+ age +"]";
+    }
+}

graphql/graphql-java/src/main/java/com/baeldung/graphql/handler/UserHandler.java

@@ -0,0 +1,56 @@
+package com.baeldung.graphql.handler;
+
+import graphql.ExecutionResult;
+import graphql.GraphQL;
+import graphql.schema.DataFetchingEnvironment;
+import ratpack.handling.Context;
+import ratpack.handling.Handler;
+
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.logging.Logger;
+
+import com.baeldung.graphql.entity.User;
+import com.baeldung.graphql.schema.UserSchema;
+import com.baeldung.graphql.utils.SchemaUtils;
+
+import static ratpack.jackson.Jackson.json;
+
+public class UserHandler implements Handler {
+    private static final Logger LOGGER = Logger.getLogger(UserHandler.class.getSimpleName());
+    private GraphQL graphql;
+    private static List<User> users = new ArrayList<>();
+
+    public UserHandler() throws Exception {
+        graphql = new GraphQL(new UserSchema().getSchema());
+    }
+
+    @Override
+    public void handle(Context context) throws Exception {
+        context.parse(Map.class)
+            .then(payload -> {
+                Map<String, Object> parameters = (Map<String, Object>) payload.get("parameters");
+                ExecutionResult executionResult = graphql.execute(payload.get(SchemaUtils.QUERY)
+                    .toString(), null, this, parameters);
+                Map<String, Object> result = new LinkedHashMap<>();
+                if (executionResult.getErrors()
+                    .isEmpty()) {
+                    result.put(SchemaUtils.DATA, executionResult.getData());
+                } else {
+                    result.put(SchemaUtils.ERRORS, executionResult.getErrors());
+                    LOGGER.warning("Errors: " + executionResult.getErrors());
+                }
+                context.render(json(result));
+            });
+    }
+
+    public static List<User> getUsers() {
+        return users;
+    }
+
+    public static List<User> getUsers(DataFetchingEnvironment env) {
+        return ((UserHandler) env.getSource()).getUsers();
+    }
+}

graphql/graphql-java/src/main/java/com/baeldung/graphql/mutation/UserMutation.java

@@ -0,0 +1,57 @@
+package com.baeldung.graphql.mutation;
+
+import graphql.annotations.GraphQLField;
+import graphql.annotations.GraphQLName;
+import graphql.schema.DataFetchingEnvironment;
+
+import javax.validation.constraints.NotNull;
+
+import com.baeldung.graphql.entity.User;
+import com.baeldung.graphql.utils.SchemaUtils;
+
+import java.util.List;
+import java.util.Optional;
+
+import static com.baeldung.graphql.handler.UserHandler.getUsers;
+
+@GraphQLName(SchemaUtils.MUTATION)
+public class UserMutation {
+    @GraphQLField
+    public static User createUser(final DataFetchingEnvironment env, @NotNull @GraphQLName(SchemaUtils.NAME) final String name, @NotNull @GraphQLName(SchemaUtils.EMAIL) final String email, @NotNull @GraphQLName(SchemaUtils.AGE) final String age) {
+        List<User> users = getUsers(env);
+        final User user = new User(name, email, Integer.valueOf(age));
+        users.add(user);
+        return user;
+    }
+
+    @GraphQLField
+    public static User updateUser(final DataFetchingEnvironment env, @NotNull @GraphQLName(SchemaUtils.ID) final String id, @NotNull @GraphQLName(SchemaUtils.NAME) final String name, @NotNull @GraphQLName(SchemaUtils.EMAIL) final String email,
+        @NotNull @GraphQLName(SchemaUtils.AGE) final String age) {
+        final Optional<User> user = getUsers(env).stream()
+            .filter(c -> c.getId() == Long.parseLong(id))
+            .findFirst();
+        if (!user.isPresent()) {
+            return null;
+        }
+        user.get()
+            .setName(name);
+        user.get()
+            .setEmail(email);
+        user.get()
+            .setAge(Integer.valueOf(age));
+        return user.get();
+    }
+
+    @GraphQLField
+    public static User deleteUser(final DataFetchingEnvironment env, @NotNull @GraphQLName(SchemaUtils.ID) final String id) {
+        final List<User> users = getUsers(env);
+        final Optional<User> user = users.stream()
+            .filter(c -> c.getId() == Long.parseLong(id))
+            .findFirst();
+        if (!user.isPresent()) {
+            return null;
+        }
+        users.removeIf(c -> c.getId() == Long.parseLong(id));
+        return user.get();
+    }
+}

graphql/graphql-java/src/main/java/com/baeldung/graphql/query/UserQuery.java

@@ -0,0 +1,42 @@
+package com.baeldung.graphql.query;
+
+import graphql.annotations.GraphQLField;
+import graphql.annotations.GraphQLName;
+import graphql.schema.DataFetchingEnvironment;
+
+import javax.validation.constraints.NotNull;
+
+import com.baeldung.graphql.entity.User;
+import com.baeldung.graphql.utils.SchemaUtils;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
+import static com.baeldung.graphql.handler.UserHandler.getUsers;
+
+@GraphQLName(SchemaUtils.QUERY)
+public class UserQuery {
+
+    @GraphQLField
+    public static User retrieveUser(final DataFetchingEnvironment env, @NotNull @GraphQLName(SchemaUtils.ID) final String id) {
+        final Optional<User> any = getUsers(env).stream()
+            .filter(c -> c.getId() == Long.parseLong(id))
+            .findFirst();
+        return any.orElse(null);
+    }
+
+    @GraphQLField
+    public static List<User> searchName(final DataFetchingEnvironment env, @NotNull @GraphQLName(SchemaUtils.NAME) final String name) {
+        return getUsers(env).stream()
+            .filter(c -> c.getName()
+                .contains(name))
+            .collect(Collectors.toList());
+    }
+
+    @GraphQLField
+    public static List<User> listUsers(final DataFetchingEnvironment env) {
+        return getUsers(env);
+    }
+
+}

graphql/graphql-java/src/main/java/com/baeldung/graphql/schema/UserSchema.java

@@ -0,0 +1,24 @@
+package com.baeldung.graphql.schema;
+
+import graphql.annotations.GraphQLAnnotations;
+import graphql.schema.GraphQLSchema;
+
+import static graphql.schema.GraphQLSchema.newSchema;
+
+import com.baeldung.graphql.mutation.UserMutation;
+import com.baeldung.graphql.query.UserQuery;
+
+public class UserSchema {
+
+    private final GraphQLSchema schema;
+
+    public UserSchema() throws IllegalAccessException, NoSuchMethodException, InstantiationException {
+        schema = newSchema().query(GraphQLAnnotations.object(UserQuery.class))
+            .mutation(GraphQLAnnotations.object(UserMutation.class))
+            .build();
+    }
+
+    public GraphQLSchema getSchema() {
+        return schema;
+    }
+}

graphql/graphql-java/src/main/java/com/baeldung/graphql/utils/SchemaUtils.java

@@ -0,0 +1,14 @@
+package com.baeldung.graphql.utils;
+
+public class SchemaUtils {
+    public static final String USER = "user";
+    public static final String ID = "id";
+    public static final String NAME = "name";
+    public static final String EMAIL = "email";
+    public static final String AGE = "age";
+
+    public static final String MUTATION = "mutation";
+    public static final String QUERY = "query";
+    public static final String ERRORS = "errors";
+    public static final String DATA = "data";
+}