Instrumentation拦截器
通过实现Instrumentation接口,可以观察一个query的执行,或修改运行期的行为。
最常见的用途是进行性能监控,和自定义日志记录,但它也可以用于完成其他任务。
创建GraphQL对象时,可以绑定相关的Instrumentation实现。
GraphQL.newGraphQL(schema)
.instrumentation(new TracingInstrumentation())
.build();
自定义Instrumentation拦截器
Instrumentation实现类需要实现"begin"开头的方法。这个方法会在查询执行的过程中,在每个步骤开始之前被调用。
每个回调方法都必须返回一个非空的InstrumentationContext对象,这个对象在本执行步骤完成时会被回调,并告知是否调用成功或是出错(可以获取Throwable对象)。
下面的示例中,给出了一个自定义的Instrumentation拦截器。可以用来测量执行过程的整体执行时间,并将结果存入一个有状态的对象当中。
class CustomInstrumentationState implements InstrumentationState {
private Map<String, Object> anyStateYouLike = new HashMap<>();
void recordTiming(String key, long time) {
anyStateYouLike.put(key, time);
}
}
class CustomInstrumentation extends SimpleInstrumentation {
@Override
public InstrumentationState createState() {
//
// instrumentation state is passed during each invocation of an Instrumentation method
// and allows you to put stateful data away and reference it during the query execution
//
return new CustomInstrumentationState();
}
@Override
public InstrumentationContext<ExecutionResult> beginExecution(InstrumentationExecutionParameters parameters) {
long startNanos = System.nanoTime();
return new SimpleInstrumentationContext<ExecutionResult>() {
@Override
public void onCompleted(ExecutionResult result, Throwable t) {
CustomInstrumentationState state = parameters.getInstrumentationState();
state.recordTiming(parameters.getQuery(), System.nanoTime() - startNanos);
}
};
}
@Override
public DataFetcher<?> instrumentDataFetcher(DataFetcher<?> dataFetcher, InstrumentationFieldFetchParameters parameters) {
//
// this allows you to intercept the data fetcher used to fetch a field and provide another one, perhaps
// that enforces certain behaviours or has certain side effects on the data
//
return dataFetcher;
}
@Override
public CompletableFuture<ExecutionResult> instrumentExecutionResult(ExecutionResult executionResult, InstrumentationExecutionParameters parameters) {
//
// this allows you to instrument the execution result some how. For example the Tracing support uses this to put
// the `extensions` map of data in place
//
return CompletableFuture.completedFuture(executionResult);
}
}
链式Instrumentation拦截器
可以使用ChainedInstrumentation类,将多个Instrumentation对象进行聚合。ChainedInstrumentation类接收一个Instrumentation对象列表参数,然后按照它们定义的顺序依次调用。
List<Instrumentation> chainedList = new ArrayList<>();
chainedList.add(new FooInstrumentation());
chainedList.add(new BarInstrumentation());
ChainedInstrumentation chainedInstrumentation = new ChainedInstrumentation(chainedList);
GraphQL.newGraphQL(schema)
.instrumentation(chainedInstrumentation)
.build();
字段验证Instrumentation
FieldValidationInstrumentation拦截器,可以在执行查询前,校验字段和字段参数。如果校验失败,那么执行过程将终止,error信息添加到查询的result当中。
可以自定义FieldValidation的实现,或直接使用SimpleFieldValidation类来为每个字段增加校验规则。
ExecutionPath fieldPath = ExecutionPath.parse("/user");
FieldValidation fieldValidation = new SimpleFieldValidation()
.addRule(fieldPath, new BiFunction<FieldAndArguments, FieldValidationEnvironment, Optional<GraphQLError>>() {
@Override
public Optional<GraphQLError> apply(FieldAndArguments fieldAndArguments, FieldValidationEnvironment environment) {
String nameArg = fieldAndArguments.getFieldArgument("name");
if (nameArg.length() > 255) {
return Optional.of(environment.mkError("Invalid user name", fieldAndArguments));
}
return Optional.empty();
}
});
FieldValidationInstrumentation instrumentation = new FieldValidationInstrumentation(
fieldValidation
);
GraphQL.newGraphQL(schema)
.instrumentation(instrumentation)
.build();