SpringMVC—异常处理

SpringMVC异常处理

一、引言

  一般项目开发中有两类异常：

• 预期异常
• 运行时异常

其中预期异常一般是由程序员主动抛出的异常，而运行时异常很难控制，只能通过规范代码编写、增加测试等手段来减少该类异常。

  通常项目是分层开发的，由外到内可分为前端项目、前端控制器、控制层、业务层、持久层。如果在控制层、业务层或持久层出现异常，SpringMVC框架如何处理呢？我们可以在前端控制器中定义全局异常处理器，之后如果控制层、业务层或持久层出现异常，直接往外抛异常即可。关于全局异常处理器，有如下定义方法：

  1. 基于注解的异常处理
  2. 基于配置的异常处理

二、示例

2.1 基于注解的异常处理

  首先，定义一个业务异常，该异常作为预期异常在项目中手动抛出。

public class CustomException extends RuntimeException {
	
    private AppHttpCodeEnum appHttpCodeEnum;

    public CustomException(AppHttpCodeEnum appHttpCodeEnum){
        this.appHttpCodeEnum = appHttpCodeEnum;
    }

    public AppHttpCodeEnum getAppHttpCodeEnum() {
        return appHttpCodeEnum;
    }
}

其中AppHttpCodeEnum类是一个枚举类，用于指定http响应状态码和响应信息，定义如下。

public enum AppHttpCodeEnum {

    // 成功段0
    SUCCESS(200,"操作成功"),
    // 登录段1~50
    NEED_LOGIN(1,"需要登录后操作"),
    LOGIN_PASSWORD_ERROR(2,"密码错误"),
    // TOKEN50~100
    TOKEN_INVALID(50,"无效的TOKEN"),
    TOKEN_EXPIRE(51,"TOKEN已过期"),
    TOKEN_REQUIRE(52,"TOKEN是必须的"),
    // SIGN验签 100~120
    SIGN_INVALID(100,"无效的SIGN"),
    SIG_TIMEOUT(101,"SIGN已过期"),
    // 参数错误 500~1000
    PARAM_REQUIRE(500,"缺少参数"),
    PARAM_INVALID(501,"无效参数"),
    PARAM_IMAGE_FORMAT_ERROR(502,"图片格式有误"),
    SERVER_ERROR(503,"服务器内部错误"),
    // 数据错误 1000~2000
    DATA_EXIST(1000,"数据已经存在"),
    AP_USER_DATA_NOT_EXIST(1001,"用户数据不存在"),
    DATA_NOT_EXIST(1002,"数据不存在"),
    // 数据错误 3000~3500
    NO_OPERATOR_AUTH(3000,"无权限操作"),
    NEED_ADMIND(3001,"需要管理员权限");

    int code;
    String errorMessage;

    AppHttpCodeEnum(int code, String errorMessage){
        this.code = code;
        this.errorMessage = errorMessage;
    }

    public int getCode() {
        return code;
    }

    public String getErrorMessage() {
        return errorMessage;
    }
}

之后，通过@ControllerAdvice和@ExceptionHandler注解定义全局异常处理器，分别捕获自定义的业务异常和不可控异常。

@ControllerAdvice  //控制器增强类
public class ExceptionCatch {

    /**
     * 处理不可控异常
     * @param e
     * @return
     */
    @ExceptionHandler(Exception.class)
    @ResponseBody
    public ResponseResult exception(Exception e){
        e.printStackTrace();
        return ResponseResult.errorResult(AppHttpCodeEnum.SERVER_ERROR);
    }

    /**
     * 处理可控异常  自定义异常
     * @param e
     * @return
     */
    @ExceptionHandler(CustomException.class)
    @ResponseBody
    public ResponseResult exception(CustomException e){
        return ResponseResult.errorResult(e.getAppHttpCodeEnum());
    }
} 

其中ResponseResult类是一个向前端返回的统一结果类。

public class ResponseResult<T> implements Serializable {

    private String host;

    private Integer code;

    private String errorMessage;

    private T data;

    public ResponseResult() {
        this.code = 200;
    }

    public ResponseResult(Integer code, T data) {
        this.code = code;
        this.data = data;
    }

    public ResponseResult(Integer code, String msg, T data) {
        this.code = code;
        this.errorMessage = msg;
        this.data = data;
    }

    public ResponseResult(Integer code, String msg) {
        this.code = code;
        this.errorMessage = msg;
    }

    public static ResponseResult errorResult(int code, String msg) {
        ResponseResult result = new ResponseResult(code, msg);
        return result;
    }


    public static ResponseResult errorResult(AppHttpCodeEnum enums) {
        return setAppHttpCodeEnum(enums, enums.getErrorMessage());
    }

    public static ResponseResult errorResult(AppHttpCodeEnum enums, String errorMessage) {
        return setAppHttpCodeEnum(enums, errorMessage);
    }

    public static ResponseResult okResult(int code, String msg) {
        ResponseResult result = new ResponseResult(code, msg);
        return result;
    }

    public static ResponseResult okResult(Object data) {
        ResponseResult result = setAppHttpCodeEnum(AppHttpCodeEnum.SUCCESS, AppHttpCodeEnum.SUCCESS.getErrorMessage());
        if (data != null) {
            result.setData(data);
        }
        return result;
    }

    public static ResponseResult okResult(AppHttpCodeEnum enums) {
        ResponseResult result = setAppHttpCodeEnum(enums);
        return result;
    }


    public static ResponseResult setAppHttpCodeEnum(AppHttpCodeEnum enums) {
        return okResult(enums.getCode(), enums.getErrorMessage());
    }

    private static ResponseResult setAppHttpCodeEnum(AppHttpCodeEnum enums, String errorMessage) {
        return okResult(enums.getCode(), errorMessage);
    }

    public Integer getCode() {
        return code;
    }

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

    public String getErrorMessage() {
        return errorMessage;
    }

    public void setErrorMessage(String errorMessage) {
        this.errorMessage = errorMessage;
    }

    public T getData() {
        return data;
    }

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

    public String getHost() {
        return host;
    }

    public void setHost(String host) {
        this.host = host;
    }
}

2.2 基于配置的异常处理

  SpringMVC提供了一个自定义异常处理器的接口，我们通过实现@HandlerExceptionResolver接口来捕获异常。

public class GlobalExceptionResolver implements HandlerExceptionResolver {
​
    @Override
    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler,
            Exception exception) {
        //根据实际业务编写代码
        return null;
    }
}

然后在spring配置文件中配置刚才新建的全局异常处理器，或者加上@Component注解。

<!--全局异常捕捉 -->
<bean class="包名.GlobalExceptionResolver" />