Graphql Java hello world：将子模式添加到父模式失败

我正在尝试原型GraphQL Java( https://github.com/andimarek/graphql-java)并开始从hello world示例构建它.我正在使用GraphiQL来调用带有模式的graphQL服务,它适用于模式{hello1},但不适用于模式{testPojo}.请找到我在下面运行的代码.有人可以让我知道下面的代码有什么问题.

static GraphQLSchema schema = null;
 /**
  * POJO to be returned for service method 2
  * @author 
  *
  */
 private class TestPojo {
     String id;
     String name;

     TestPojo(String id,String name) {
         this.id = id;
         this.name = name;
     }

     public String getId() {
         return id;
     }

     public void setId(String id) {
         this.id = id;
     }

     public String getName() {
        return name;
     }

     public void setName(String name) {
         this.name = name;
     }
 }

/**
 * service method 1
 * @return
 */
public String greeting1() {
    return "Hello123";
 }

/**
 * service method 2
 * @return
 */
public TestPojo greeting2() {
    return new TestPojo("1","Jack");
}


/**
 * GraphQl endpoint invoked using GraphiQl
 * @param query
 * @return
 */
@RequestMapping("/query")
public Object testGraphQLWithQuery(@RequestParam("query") String query) {
    return new GraphQL(schema).execute(query).getData();
}

// Schema definition for graphQL
static {

    // sub schema to be added to parent  schema
     GraphQLObjectType testPojo = newObject().name("TestPojo").description("This is a test POJO")
            .field(newFieldDefinition().name("id").type(GraphQLString).build())
            .field(newFieldDefinition().name("name").type(GraphQLString).build())
            .build();


    // parent schema
    GraphQLObjectType queryType = newObject().name("helloWorldQuery")
            .field(newFieldDefinition().type(GraphQLString).name("hello1").dataFetcher(new DataFetcher() {

                @Override
                public Object get(DataFetchingEnvironment arg0) {
                    Object a = new GrapgQLSampleController().greeting1();
                    return a;
                }
            }).build())
            .field(newFieldDefinition().type(testPojo).name("testPojo").dataFetcher(new DataFetcher() {

                @Override
                public Object get(DataFetchingEnvironment arg0) {
                    Object a = new GrapgQLSampleController().greeting2();
                    return a;
                }
            }).build())
            .build();

     schema = GraphQLSchema.newSchema().query(queryType).build();
}