springboot统一接口返回数据

一，没有异常的情况，正常返回数据

希望接口统一返回的数据格式如下：

{
    "status": 0,
    "msg": "成功",
    "data": null
}

和接口数据对应的bean

/**
 * 统一返回结果的实体
 * @param <T>
 */
public class Result<T> implements Serializable {

    private static final long serialVersionUID = 1L;

    /**
     * 错误码
     */
    private int status;

    /**
     * 提示消息
     */
    private String msg;

    /**
     * 返回的数据体
     */
    private T data;

    public int getStatus() {
        return status;
    }

    public void setStatus(int status) {
        this.status = status;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }
}

操作Result实体的工具类

/**
 * 生成result的工具类，避免重复代码
 */
public class ResultUtils {

    /**
     * 成功时生成result的方法,有返回数据
     */
    public static <T> Result<T> success(T t){
        Result<T> result = new Result<>();
        result.setStatus(ResultEnum.SUCCESS.getCode());
        result.setMsg(ResultEnum.SUCCESS.getMsg());
        result.setData(t);
        return result;
    }

    /**
     * 成功时生成result的方法,无返回数据
     */
    public static <T> Result<T> success(){
        return success(null);
    }

    /**
     * 失败时生成result的方法
     */
    public static <T> Result<T> error(int status, String msg){
        Result<T> result = new Result<>();
        result.setStatus(status);
        result.setMsg(msg);
        return result;
    }

}

封装错误码和错误消息的枚举类

/**
 * 所有返回结果的枚举
 */
public enum ResultEnum {

    UNKNOWN_ERROR(-1, "未知错误"),
    SUCCESS(0, "成功"),
    BASIC_INFO_ID_IS_EMPTY(600, "基本信息中BasicInfoId为空"),
    BASIC_INFO_ADD_TO_DATABASE_FAILURE(601, "向数据库添加基本信息失败"),
    DETAILS_DATA_BASIC_INFO_ID_IS_EMPTY(602, "测试数据中BasicInfoId为空"),
    DETAILS_DATA_ADD_TO_DATABASE_FAILURE(603, "向数据库添加测试数据失败");

    ResultEnum(int code, String msg) {
        this.code = code;
        this.msg = msg;
    }

    private int code;

    private String msg;

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    @Override
    public String toString() {
        return "ResultEnum{" +
                "code=" + code +
                ", msg='" + msg + '\'' +
                '}';
    }

}

统一封装返回结果的切面

之所以需要这个切面，是为了避免每个Controller方法中都要调用ResultUtils.success()。有了这个切面，Controller可以和原来一样正常返回对象，字符串，void，在切面里面将结果封装成Result实体，而不需要每个Controller方法都返回Result实体。

/**
 * 统一处理返回结果的切面，避免每个controller方法里面都要调用ResultUtils.success()这句话
 * 统一在这个切面里面调用
 */
@ControllerAdvice
public class MyResponseAdvice implements ResponseBodyAdvice<Object> {

    @Autowired
    private ObjectMapper objectMapper;

    /**
     * Whether this component supports the given controller method return type
     * and the selected {@code HttpMessageConverter} type.
     *
     * @param returnType    the return type
     * @param converterType the selected converter type
     * @return {@code true} if {@link #beforeBodyWrite} should be invoked;
     * {@code false} otherwise
     */
    @Override
    public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {
        return true;
    }

    /**
     * Invoked after an {@code HttpMessageConverter} is selected and just before
     * its write method is invoked.
     *
     * @param body                  the body to be written
     * @param returnType            the return type of the controller method
     * @param selectedContentType   the content type selected through content negotiation
     * @param selectedConverterType the converter type selected to write to the response
     * @param request               the current request
     * @param response              the current response
     * @return the body that was passed in or a modified (possibly new) instance
     */
    @Override
    public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) {
        if(body instanceof Result){ //发生异常之后，异常处理器里面返回的已经是Result了
            return body;
        }else if(body instanceof String){ //String属于特殊情况，需要单独处理，否则会报错
            try {
                return objectMapper.writeValueAsString(ResultUtils.success(body));
            } catch (JsonProcessingException e) {
                e.printStackTrace();
                return ResultUtils.error(ResultEnum.UNKNOWN_ERROR.getCode(), e.getMessage());
            }
        }
        return ResultUtils.success(body);
    }
}

 

---

二，有异常的情况下

    service层为了自动回滚事务，会抛出一些自定义的RuntimeException。默认情况下，只有RuntimeException才会回滚事务。如果Controller里面直接处理service层抛出的异常，则Controller里面到处都是try catch块，代码会很难看。将异常集中在一个地方处理会好很多。
    springboot中是通过@ControllerAdvice和@ExceptionHandler来完成统一异常处理的。这2个注解只能处理Controller和拦截器中抛出的异常，其他地方抛出的异常（比如Filter中抛出的异常），无法捕获。其他地方抛出的异常会转到/error的Controller方法来处理，默认是BasicErrorController来处理，为了能处理其他地方抛出的异常，我们会自定义ErrorController。

统一的异常处理类，处理Controller和拦截器抛出的异常

/**
 * 统一的异常处理类
 */
@ControllerAdvice
public class MyExceptionHandler {

    /**
     * 转发到/error，表示由BasicErrorController处理，
     * BasicErrorController是由springboot自动装配到容器中的
     */
    /*@ExceptionHandler(BasicInfoException.class)
    public String handleException(Exception ex, HttpServletRequest request){
        request.setAttribute("javax.servlet.error.status_code", 401);
        request.setAttribute("exMsg", ex.getMessage());
        return "forward:/error";
    }*/


    /**
     * 处理基本信息相关的异常
     */
    @ExceptionHandler(BasicInfoException.class)
    @ResponseBody
    public Result handleBasicInfoException(BasicInfoException ex){
        return ResultUtils.error(ex.getCode(), ex.getMessage());
    }

    /**
     * 处理测试数据相关的异常
     */
    @ExceptionHandler(DetailsDataException.class)
    @ResponseBody
    public Result handleDetailsDataException(DetailsDataException ex){
        return ResultUtils.error(ex.getCode(), ex.getMessage());
    }


    /**
     * 处理未知异常
     */
    @ExceptionHandler(Exception.class)
    @ResponseBody
    public Result handleUnKnowException(Exception ex){
        return ResultUtils.error(ResultEnum.UNKNOWN_ERROR.getCode(), ex.getMessage());
    }

}

自定义的异常类示例

public class BasicInfoException extends RuntimeException {

    private int code;

    public BasicInfoException(int code, String msg){
        super(msg);
        this.code = code;
    }

    public int getCode() {
        return code;
    }
}

处理其他地方抛出的异常（不是Controller和拦截器抛出的异常）,自定义ErrorController

/**
 * 自定义ErrorController，处理其他地方抛出的异常（不是Controller和拦截器抛出的异常）
 */
@Controller
public class MyBasicErrorController extends AbstractErrorController {

    private Logger logger = LoggerFactory.getLogger(this.getClass());

    /**
     * 可以通过@Value获取到
     */
    @Value("${server.error.path}")
    private String myPath;

    private final ErrorProperties errorProperties;

    private ErrorAttributes mErrorAttributes;

    public MyBasicErrorController(ErrorAttributes errorAttributes, ServerProperties serverProperties) {
        super(errorAttributes);
        this.errorProperties = serverProperties.getError();
        this.mErrorAttributes = errorAttributes;
    }

    //@RequestMapping(value = "/error")
    @RequestMapping("${server.error.path}") //从properties文件中获取
    @ResponseBody
    public Result<Object> error(HttpServletRequest request) throws Throwable {
        logger.debug("myPath = " + myPath);

        //发生错误之后直接将异常抛出去，异常会到统一异常处理器中处理
        WebRequest webRequest = new ServletWebRequest(request);
        Throwable throwable = this.mErrorAttributes.getError(webRequest).getCause();
        throw throwable;
        /*UserException ex;
        if(throwable instanceof UserException){
            ex = (UserException) throwable;
            throw ex;
        }else{
            throw throwable;
        }*/
        /*HttpStatus status = getStatus(request);
        if (status == HttpStatus.NO_CONTENT) {
            return ResultUtils.error(status.value(), status.name());
        }
        Map<String, Object> body = getErrorAttributes(request, isIncludeStackTrace(request, MediaType.ALL));
        return ResultUtils.error((Integer) body.get("status"), (String)body.get("message"));*/
    }

    /**
     * Determine if the stacktrace attribute should be included.
     * @param request the source request
     * @param produces the media type produced (or {@code MediaType.ALL})
     * @return if the stacktrace attribute should be included
     */
    private boolean isIncludeStackTrace(HttpServletRequest request, MediaType produces) {
        ErrorProperties.IncludeStacktrace include = getErrorProperties().getIncludeStacktrace();
        if (include == ErrorProperties.IncludeStacktrace.ALWAYS) {
            return true;
        }
        if (include == ErrorProperties.IncludeStacktrace.ON_TRACE_PARAM) {
            return getTraceParameter(request);
        }
        return false;
    }

    /**
     * Provide access to the error properties.
     * @return the error properties
     */
    private ErrorProperties getErrorProperties() {
        return this.errorProperties;
    }


    /**
     * Returns the path of the error page.
     *
     * @return the error path
     */
    @Override
    public String getErrorPath() {
        return this.errorProperties.getPath();
    }
}

 

自定义ErrorController中错误处理的方法中，也可以直接将异常抛出，这样异常就会交给统一异常处理器进行处理。

 //@RequestMapping(value = "/error")
    @RequestMapping("${server.error.path}") //从properties文件中获取
    @ResponseBody
    public Result<Object> error(HttpServletRequest request) throws Throwable {
        logger.debug("myPath = " + myPath);

        //发生错误之后直接将异常抛出去，异常会到统一异常处理器中处理
        WebRequest webRequest = new ServletWebRequest(request);
        Throwable throwable = this.mErrorAttributes.getError(webRequest).getCause();
        UserException ex;
        if(throwable instanceof UserException){
            ex = (UserException) throwable;
            throw ex;
        }else{
            throw throwable;
        }
        /*HttpStatus status = getStatus(request);
        if (status == HttpStatus.NO_CONTENT) {
            return ResultUtils.error(status.value(), status.name());
        }
        Map<String, Object> body = getErrorAttributes(request, isIncludeStackTrace(request, MediaType.ALL));
        return ResultUtils.error((Integer) body.get("status"), (String)body.get("message"));*/
    }