graphql-java关键组成部分DataFetcher、TypeResolver、RuntimWiring的使用

graphql-java关键组成部分DataFetcher、TypeResolver、RuntimWiring的使用

21 2018-09-25 14:21:12

##DataFetcher
用于获取数据
动态获取可使用匿名实现DataFetcher
```
environment -> rockmanService.getHerosFromSeries(environment.getArgument("series"))
```
静态内容可使用静态实现类StaticDataFetcher
##TypeResolver
为SDL的Interface或Union设置TypeResolver，用于泛型的向下转型
```java
new TypeResolver() {
	@Override
	public GraphQLObjectType getType(TypeResolutionEnvironment env) {
		Object obj = env.getObject();
		if (obj instanceof Doctor) {
			return env.getSchema().getObjectType("Doctor");
		} else if (obj instanceof Hunter) {
			return env.getSchema().getObjectType("Hunter");
		} else if (obj instanceof Enemy) {
			return env.getSchema().getObjectType("Enemy");
		}
		return null;
	}
};
```
##RuntimeWiring
最重要最关键的数据绑定部分
```
RuntimeWiring.newRuntimeWiring()
	.type("QueryType", builder -> builder
		.dataFetcher("hero", environment -> rockmanService.getHerosFromSeries(environment.getArgument("series")))
		.dataFetcher("hunter", environment -> rockmanService.getHunterFromName(environment.getArgument("name")))
		.dataFetcher("enemy", environment -> rockmanService.getEnemyFromName(environment.getArgument("name")))
		)
		.type("Hunter", builder -> builder
			.dataFetcher("enemies", environment -> rockmanService.getEnemies())
		)
		.type(
			newTypeWiring("Character")
				.typeResolver(typeResolver)
				.build()
		)
		.build();
// 第一个type绑定对应查询入口，即SDL中的
type QueryType {
	hero(series: Series): Character
	hunter(name: String): Hunter
	enemy(name: String): Enemy
}
// 第二个type绑定对应查询结果中非基本类型的子查询，即SDL定义的enemies，结果是Character，需要二次查询
type Hunter implements Character {
	id: ID!
	name: String!
	enemies: [Character]
	appearsIn: [Series]!
}
// 第三个type绑定是为了给interface Character绑定一个TypeResolver，基本是instanceof
```