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原因
在springboot项目里我们希望接口返回的数据包含至少三个属性：
code：请求接口的返回码，成功或者异常等返回编码，例如定义请求成功。
message：请求接口的描述，也就是对返回编码的描述。
data：请求接口成功，返回的结果。
{
"code":20000,
"message":"成功",
"data":{
"info":"测试成功"
}
}
开发环境
工具：IDEA
SpringBoot版本：2.2.2.RELEASE
依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<!-- fastjson -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.62</version>
</dependency>
<!-- Spring web -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- lombok -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
<!-- swagger3 -->
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-boot-starter</artifactId>
<version>3.0.0</version>
</dependency>
创建 SpringBoot 工程
新建 SpringBoot 项目common_utils，包名com.spring.utils
返回结果统一
创建code枚举
在com.spring.utils中创建 pojo 包，并添加枚举ResultCode
public enum ResultCode {
/* 成功状态码 */
SUCCESS(20000, "成功"),
/* 参数错误 */
PARAM_IS_INVALID(1001, "参数无效"),
PARAM_IS_BLANK(1002, "参数为空"),
PARAM_TYPE_BIND_ERROR(1003, "参数类型错误"),
PARAM_NOT_COMPLETE(1004, "参数缺失"),
/* 用户错误 2001-2999*/
USER_NOTLOGGED_IN(2001, "用户未登录"),
USER_LOGIN_ERROR(2002, "账号不存在或密码错误"),
SYSTEM_ERROR(10000, "系统异常，请稍后重试");
private Integer code;
private String message;
private ResultCode(Integer code, String message) {
this.code = code;
this.message = message;
}
public Integer code() {
return this.code;
}
public String message() {
return this.message;
}
}
可根据项目自定义，结果返回码
创建返回结果实体
在 pojo 包中添加返回结果类R
@Data
@ApiModel(value = "返回结果实体类", description = "结果实体类")
public class R implements Serializable {
private static final long serialVersionUID = 1L;
@ApiModelProperty(value = "返回码")
private Integer code;
@ApiModelProperty(value = "返回消息")
private String message;
@ApiModelProperty(value = "返回数据")
private Object data;
private R() {
}
public R(ResultCode resultCode, Object data) {
this.code = resultCode.code();
this.message = resultCode.message();
this.data = data;
}
private void setResultCode(ResultCode resultCode) {
this.code = resultCode.code();
this.message = resultCode.message();
}
// 返回成功
public static R success() {
R result = new R();
result.setResultCode(ResultCode.SUCCESS);
return result;
}
// 返回成功
public static R success(Object data) {
R result = new R();
result.setResultCode(ResultCode.SUCCESS);
result.setData(data);
return result;
}
// 返回失败
public static R fail(Integer code, String message) {
R result = new R();
result.setCode(code);
result.setMessage(message);
return result;
}
// 返回失败
public static R fail(ResultCode resultCode) {
R result = new R();
result.setResultCode(resultCode);
return result;
}
}
自定义一个注解
新建包annotation，并添加ResponseResult注解类
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.TYPE, ElementType.METHOD})
@Documented
public @interface ResponseResult {
}
定义拦截器
新建包interceptor，并添加ResponseResultInterceptorJava类
@Component
public class ResponseResultInterceptor implements HandlerInterceptor {
//标记名称
public static final String RESPONSE_RESULT_ANN = "RESPONSE-RESULT-ANN";
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception {
// TODO Auto-generated method stub
if (handler instanceof HandlerMethod) {
final HandlerMethod handlerMethod = (HandlerMethod) handler;
final Class<?> clazz = handlerMethod.getBeanType();
final Method method = handlerMethod.getMethod();
// 判断是否在类对象上添加了注解
if (clazz.isAnnotationPresent(ResponseResult.class)) {
// 设置此请求返回体，需要包装，往下传递，在ResponseBodyAdvice接口进行判断
request.setAttribute(RESPONSE_RESULT_ANN, clazz.getAnnotation(ResponseResult.class));
} else if (method.isAnnotationPresent(ResponseResult.class)) {
request.setAttribute(RESPONSE_RESULT_ANN, method.getAnnotation(ResponseResult.class));
}
}
return true;
}
}
用于拦截请求，判断 Controller 是否添加了@ResponseResult注解
注册拦截器
新建包config，并添加WebAppConfig配置类
@Configuration
public class WebAppConfig implements WebMvcConfigurer {
// SpringMVC 需要手动添加拦截器
@Override
public void addInterceptors(InterceptorRegistry registry) {
ResponseResultInterceptor interceptor = new ResponseResultInterceptor();
registry.addInterceptor(interceptor);
WebMvcConfigurer.super.addInterceptors(registry);
}
}
方法返回值拦截处理器
新建包handler，并添加ResponseResultHandler配置类，实现ResponseBodyAdvice重写两个方法
import org.springframework.web.method.HandlerMethod;
/**
* 使用 @ControllerAdvice & ResponseBodyAdvice
* 拦截Controller方法默认返回参数，统一处理返回值/响应体
*/
@ControllerAdvice
public class ResponseResultHandler implements ResponseBodyAdvice<Object> {
// 标记名称
public static final String RESPONSE_RESULT_ANN = "RESPONSE-RESULT-ANN";
// 判断是否要执行 beforeBodyWrite 方法，true为执行，false不执行，有注解标记的时候处理返回值
@Override
public boolean supports(MethodParameter arg0, Class<? extends HttpMessageConverter<?>> arg1) {
ServletRequestAttributes sra = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
HttpServletRequest request = sra.getRequest();
// 判断请求是否有包装标记
ResponseResult responseResultAnn = (ResponseResult) request.getAttribute(RESPONSE_RESULT_ANN);
return responseResultAnn == null ? false : true;
}
// 对返回值做包装处理
@Override
public Object beforeBodyWrite(Object body, MethodParameter arg1, MediaType arg2,
Class<? extends HttpMessageConverter<?>> arg3, ServerHttpRequest arg4, ServerHttpResponse arg5) {
if (body instanceof R) {
return (R) body;
} else if (body instanceof String) {
return body;
}
return R.success(body);
}
}
实现ResponseBodyAdvice重写两个方法
添加@ControllerAdvice注解
测试
新建包controller，并添加TestController测试类
@RestController
@ResponseResult
public class TestController {
@GetMapping("/test")
public Map<String, Object> test() {
HashMap<String, Object> data = new HashMap<>();
data.put("info", "测试成功");
return data;
}
}
添加@ResponseResult注解
启动项目，在默认端口: 8080
浏览器访问地址：localhost:8080/test
{"code":20000,"message":"成功","data":{"info":"测试成功"}}
总结
1、创建code枚举和返回结果实体类
2、自定义一个注解@ResponseResult
3、定义拦截器，拦截请求，判断Controller上是否添加了@ResponseResult注解。如果添加了注解在request中添加注解标记，往下传递
4、添加@ControllerAdvice注解 ，实现ResponseBodyAdvice接口，并重写两个方法，通过判断request中是否有注解标记，如果有就往下执行，进一步包装。没有就直接返回，不需包装。
问题
1、如果要返回错误结果，这种方法显然不方便
@GetMapping("/fail")
public R error() {
int res = 0; // 查询结果数
if(res == 0) {
return R.fail(10001, "没有数据");
}
return R.success(res);
}
2、我们需要对错误和异常进行进一步的封装
封装错误和异常结果
创建错误结果实体
在包pojo中添加ErrorResult实体类
/**
* 异常结果包装类
* @author sw-code
*
*/
public class ErrorResult {
private Integer code;
private String message;
private String exception;
public Integer getCode() {
return code;
}
public void setCode(Integer code) {
this.code = code;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public String getException() {
return exception;
}
public void setException(String exception) {
this.exception = exception;
}
public static ErrorResult fail(ResultCode resultCode, Throwable e, String message) {
ErrorResult errorResult = ErrorResult.fail(resultCode, e);
errorResult.setMessage(message);
return errorResult;
}
public static ErrorResult fail(ResultCode resultCode, Throwable e) {
ErrorResult errorResult = new ErrorResult();
errorResult.setCode(resultCode.code());
errorResult.setMessage(resultCode.message());
errorResult.setException(e.getClass().getName());
return errorResult;
}
public static ErrorResult fail(Integer code, String message) {
ErrorResult errorResult = new ErrorResult();
errorResult.setCode(code);
errorResult.setMessage(message);
return errorResult;
}
}
自定义异常类
在包pojo中添加BizException实体类，继承RuntimeException
@Data
public class BizException extends RuntimeException {
/**
* 错误码
*/
private Integer code;
/**
* 错误信息
*/
private String message;
public BizException() {
super();
}
public BizException(ResultCode resultCode) {
super(resultCode.message());
this.code = resultCode.code();
this.message = resultCode.message();
}
public BizException(ResultCode resultCode, Throwable cause) {
super(resultCode.message(), cause);
this.code = resultCode.code();
this.message = resultCode.message();
}
public BizException(String message) {
super(message);
this.code = -1;
this.message = message;
}
public BizException(Integer code, String message) {
super(message);
this.code = code;
this.message = message;
}
public BizException(Integer code, String message, Throwable cause) {
super(message, cause);
this.code = code;
this.message = message;
}
@Override
public synchronized Throwable fillInStackTrace() {
return this;
}
}
全局异常处理类
在包handler中添加GlobalExceptionHandler，添加@RestControllerAdvice注解
/**
* 全局异常处理类
* @RestControllerAdvice(@ControllerAdvice)，拦截异常并统一处理
* @author sw-code
*
*/
@Slf4j
@RestControllerAdvice
public class GlobalExceptionHandler {
/**
* 处理自定义的业务异常
* @param e 异常对象
* @param request request
* @return 错误结果
*/
@ExceptionHandler(BizException.class)
public ErrorResult bizExceptionHandler(BizException e, HttpServletRequest request) {
log.error("发生业务异常！原因是: {}", e.getMessage());
return ErrorResult.fail(e.getCode(), e.getMessage());
}
// 拦截抛出的异常，@ResponseStatus：用来改变响应状态码
@ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
@ExceptionHandler(Throwable.class)
public ErrorResult handlerThrowable(Throwable e, HttpServletRequest request) {
log.error("发生未知异常！原因是: ", e);
ErrorResult error = ErrorResult.fail(ResultCode.SYSTEM_ERROR, e);
return error;
}
// 参数校验异常
@ExceptionHandler(BindException.class)
public ErrorResult handleBindExcpetion(BindException e, HttpServletRequest request) {
log.error("发生参数校验异常！原因是：",e);
ErrorResult error = ErrorResult.fail(ResultCode.PARAM_IS_INVALID, e, e.getAllErrors().get(0).getDefaultMessage());
return error;
}
@ExceptionHandler(MethodArgumentNotValidException.class)
public ErrorResult handleMethodArgumentNotValidException(MethodArgumentNotValidException e, HttpServletRequest request) {
log.error("发生参数校验异常！原因是：",e);
ErrorResult error = ErrorResult.fail(ResultCode.PARAM_IS_INVALID,e,e.getBindingResult().getAllErrors().get(0).getDefaultMessage());
return error;
}
}
添加注解@RestControllerAdvice(@ControllerAdvice)，拦截异常并统一处理
修改方法返回值拦截处理器
将错误和异常结果也进行统一封装
/**
* 使用 @ControllerAdvice & ResponseBodyAdvice
* 拦截Controller方法默认返回参数，统一处理返回值/响应体
*/
@ControllerAdvice
public class ResponseResultHandler implements ResponseBodyAdvice<Object> {
// 标记名称
public static final String RESPONSE_RESULT_ANN = "RESPONSE-RESULT-ANN";
// 判断是否要执行 beforeBodyWrite 方法，true为执行，false不执行，有注解标记的时候处理返回值
@Override
public boolean supports(MethodParameter arg0, Class<? extends HttpMessageConverter<?>> arg1) {
ServletRequestAttributes sra = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
HttpServletRequest request = sra.getRequest();
// 判断请求是否有包装标记
ResponseResult responseResultAnn = (ResponseResult) request.getAttribute(RESPONSE_RESULT_ANN);
return responseResultAnn == null ? false : true;
}
// 对返回值做包装处理，如果属于异常结果，则需要再包装
@Override
public Object beforeBodyWrite(Object body, MethodParameter arg1, MediaType arg2,
Class<? extends HttpMessageConverter<?>> arg3, ServerHttpRequest arg4, ServerHttpResponse arg5) {
if (body instanceof ErrorResult) {
ErrorResult error = (ErrorResult) body;
return R.fail(error.getCode(), error.getMessage());
} else if (body instanceof R) {
return (R) body;
} else if (body instanceof String) {
return body;
}
return R.success(body);
}
}
测试
@GetMapping("/fail")
public Integer error() {
int res = 0; // 查询结果数
if( res == 0 ) {
throw new BizException("没有数据");
}
return res;
}
返回结果
{"code":-1,"message":"没有数据","data":null}
我们无需担心返回类型，如果需要返回错误提示信息，可以直接抛出自定义异常(BizException)，并添加自定义错误信息。
查看源码
码云地址
