java Spring rest controller@ExceptionHandler返回xml内容和json错误

Question

所以我有一个@RestController，我想基于前端应用程序的模式返回和验证XML，以便在编辑器中显示它们。我希望错误是json格式的，以便用js处理和显示它们

@RestController
public class UserController {

    @RequestMapping(value = "/test",
        method = RequestMethod.GET,
        produces = MediaType.APPLICATION_XML_VALUE)
    public ResponseEntity<String> throwException(
        @RequestParam(value = "flag", defaultValue = "false") Boolean flag
    ) throws Exception {
        if (flag) {
            throw new Exception();
        } else {
            return ResponseEntity.ok("<xml>hello</xml>");
        }
    }


    @ResponseStatus(HttpStatus.BAD_REQUEST)
    @ExceptionHandler(Exception.class)
    @ResponseBody
    ServerError exceptionHandler(HttpServletRequest req, Exception ex) {
        return new ServerError(req.getRequestURL().toString(),ex);
    }

}

我想以JSON格式返回的ServerError：

public class ServerError {

    public final String url;
    public final String error;

    public ServerError(String url, Exception ex) {
        this.url = url;
        this.error = ex.getMessage();
    }

    public String getUrl() {
        return url;
    }

    public String getError() {
        return error;
    }
}

所以<xml>hello</xml>返回得很好，但是当我将标志设置为true时，我得到

ERROR   2017-10-18 12:56:53,189 [http-nio-0.0.0.0-8080-exec-2] org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver  - Failed to invoke @ExceptionHandler method: eu.openminted.registry.core.exception.ServerError eu.openminted.registry.service.UserController.malformedExeption(javax.servlet.http.HttpServletRequest,java.lang.Exception)
org.springframework.web.HttpMediaTypeNotAcceptableException: Could not find acceptable representation

此外，将produces同时设置为XML和JSON会产生相同的结果

@RequestMapping(value = "/test",
        method = RequestMethod.GET,
        produces = {MediaType.APPLICATION_XML_VALUE,MediaType.APPLICATION_JSON_UTF8_VALUE})

Answer 1

通过从@RequestMapping中删除produces并用ResponseEntity指定我想要返回的类型，我成功地解决了这个问题

@RequestMapping(value = "/test", method = RequestMethod.GET)
public ResponseEntity<String> throwException(
    @RequestParam(value = "flag", defaultValue = "false") Boolean flag
) throws Exception {
    if (flag) {
        throw new Exception();
    } else {
        ResponseEntity response = ResponseEntity.ok().
            contentType(MediaType.APPLICATION_XML).
            body("<xml>hello</xml>");
        return response;
    }
}

这个解决方案的问题是，所有方法都有一个@annotation与它们产生的类型相关，而这并没有破坏一致性

Answer 2

要使ExceptionHandler返回XML格式（默认情况下返回JSON格式），需要执行两个步骤：

1. 导入maven依赖项：

 <dependency>
     <groupId>com.fasterxml.jackson.dataformat</groupId>
     <artifactId>jackson-dataformat-xml</artifactId>
 </dependency>

1. 使用ResposneEntity的静态方法internalServerError()： ResponseEntity.internalServerError().header("MyHeader","MyValue").contentType(MediaType.APPLICATION_XML).body(ex);

在contentType中，指定MediaType.APPLICATION_XML