java - 如何在 Jersey 的 MessageBodyWriter 中检索资源方法注释？

Question

Jersey 2.21.

我有如下资源文件

……
@POST
@Path("/userReg")
@Produces("application/json;charset=UTF-8")
public JsonResp userReg(UserRegReq userRegReq) throws LoginNameExists {
    HttpHeaderUtils.parseHeaders(userRegReq, headers);

    //JsonResp is a custom java class.
    JsonResp result = new JsonResp();

    //will throw LoginNameExists
    User user = userManager.register(userRegReq.getLoginName(), userRegReq.getPassword());

    //success
    result.setResult(0);
result.setData(user.getId);

    return result;
}
……

为了将结果返回给客户端，我实现了一个自定义的 MessageBodyWriter，如下所示

@Produces("application/json")
public class MyRespWriter implements MessageBodyWriter<JsonResp> {

    @Override
    public boolean isWriteable(Class<?> aClass, Type type, Annotation[] annotations, MediaType mediaType) {
        return type == JsonResp.class;
    }

    @Override
    public long getSize(JsonResp jsonResp, Class<?> aClass, Type type, Annotation[] annotations, MediaType mediaType) {
        return 0;
    }

    @Override
public void writeTo(JsonResp jsonResp, Class<?> aClass, Type type, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, Object> multivaluedMap, OutputStream outputStream) throws IOException, WebApplicationException {
        //if these no exception in userReg(), 
        //the parameter annotations contains the annotations 
        //such as POST, Path, Produces;
        //but if there is an exception in userReg(), 
        //the parameter annotations contains none of POST, Path, Produces; 
        //So, is there any way to retrieve the original annotations all along?


        //JsonUtils is a custom java class.
        String data = JsonUtils.toJsonString(jsonResp);
        Writer osWriter = new OutputStreamWriter(outputStream, "UTF-8");
        osWriter.write(data);
        osWriter.flush();
    }
}

为了处理异常，我实现了一个 ExceptionMapper，如下所示:

public class MyExceptionMapper implements ExceptionMapper<Exception> {

    public Response toResponse(Exception e) {

        JsonResp result = new JsonResp();

        //error
        result.setResult(-1);
        result.setErrMsg("System error.");

        return Response.ok(result, MediaType.APPLICATION_JSON_TYPE).status(Response.Status.OK).build();
    }
}

现在，如果一切正常，没有异常，代码执行路由是userReg() -> MyRespWriter.writeTo()，MyRespWriter.writeTo()的参数“annotations” )包含userReg()方法的正确注解，如POST、Path、Produces .

但是如果userReg()抛出异常，代码执行路由是userReg() -> MyExceptionMapper.toResponse() -> MyRespWriter.writeTo()，参数方法 MyRespWriter.writeTo() 的“注释”没有方法 userReg() 的注释。

我想知道，MyRespWriter.writeTo()有什么方法可以一直检索原始注释吗？

Answer 1

你可以注入(inject)ResourceInfo ，然后通过ri.getResourceMethod()获取Method，然后调用method.getAnnotations()获取注解。

public class MyRespWriter implements MessageBodyWriter<JsonResp> {

    @Context
    ResourceInfo ri;

    ...

    Annotations[] annos = ri.getResourceMethod().getAnnotations();