graphql-java中的细节补充

graphql-java中的细节补充

19 2018-09-25 14:33:06

###DataFetchingEnvironment的方法
**<T> T getSource();**
获取返回对象
**<T> T getRoot();**
获取返回对象，top level
**Map<String, Object> getArguments();**
**boolean containsArgument(String name);**
**<T> T getArgument(String name);**
获取查询参数
**<T> T getContext();**
自定义context，可在整个query期间保持不变
GraphQLFieldDefinition getFieldDefinition();
List<Field> getFields();
Field getField();
GraphQLOutputType getFieldType();
ExecutionTypeInfo getFieldTypeInfo();
GraphQLType getParentType();
GraphQLSchema getGraphQLSchema();
Map<String, FragmentDefinition> getFragmentsByName();
ExecutionId getExecutionId();
DataFetchingFieldSelectionSet getSelectionSet();
ExecutionContext getExecutionContext();
###DataFetchingFieldSelectionSet
用于判断查询内容，可以使用通配符
```java
DataFetcher smartUserDF = new DataFetcher() {
	@Override
	public Object get(DataFetchingEnvironment env) {
		String userId = env.getArgument("userId");
		DataFetchingFieldSelectionSet selectionSet = env.getSelectionSet();
		if (selectionSet.contains("user/*")) {
			return getUserAndTheirFriends(userId);
		} else {
			return getUser(userId);
		}
	}
};
DataFetchingFieldSelectionSet selectionSet = env.getSelectionSet();
List<SelectedField> nodeFields = selectionSet.getFields("edges/nodes/*");
nodeFields.forEach(selectedField -> {
	System.out.println(selectedField.getName());
	System.out.println(selectedField.getFieldDefinition().getType());
	DataFetchingFieldSelectionSet innerSelectionSet = selectedField.getSelectionSet();
	// this forms a tree of selection and you can get very fancy with it
}
```