JAVA高级面试进阶训练营视频教程

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定义统一异常类：BusinessException.java

package com.miaoying;

import lombok.Data;

@Data
public class BusinessException extends RuntimeException {

    /**
     * 错误码
     */
    private Integer code;

    /**
     * 错误信息
     */
    private String message;

    public BusinessException(Integer code, String message) {
        super(message);
        this.code = code;
        this.message = message;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        BusinessException that = (BusinessException) o;

        if (!code.equals(that.code)) return false;
        return message.equals(that.message);

    }

    @Override
    public int hashCode() {
        int result = code != null ? code.hashCode() : 0;
        result = 31 * result + (message != null ? message.hashCode() : 0);
        return result;
    }
}

定义统一的数据返回的结构：ResultResponse<T>.java

package com.miaoying;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class ResultResponse<T> implements Serializable {

    private static final long serialVersionUID = 5261844042861308860L;
    private int retCode;

    private String retMsg;

    private T rsp;

    public static <T> ResultResponse<T> wrapSuccessfulResult(T data) {
        ResultResponse<T> result = new ResultResponse<T>();
        result.rsp = data;
        result.retCode = 200;
        result.retMsg = "ok";
        return result;
    }
}

定义异常拦截器：BusinessExceptionFilter.java

package com.miaoying

import com.miaoying.BusinessException;
import com.miaoying.ResultResponse;
import com.alibaba.fastjson.JSONObject;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletRequest;

@ControllerAdvice
@Slf4j
public class BusinessExceptionFilter {

    @ExceptionHandler(BusinessException.class)
    @ResponseBody
    public Object handleBusinessException(HttpServletRequest request, BusinessException ex) {
        log.error("BusinessException code:{},msg:{}", ex.getCode(), ex.getMessage());
        ResultResponse response = new ResultResponse(ex.getCode(), ex.getMessage(), null);
        return JSONObject.toJSON(response);
    }

    @ExceptionHandler(Exception.class)
    @ResponseBody
    public Object handleException(HttpServletRequest request, Exception ex) {
        log.error("Exception code:{},msg:{}", 500, ex.getMessage());
        ResultResponse response = new ResultResponse(500, "目前业务繁忙，请您稍后！", null);
        return JSONObject.toJSON(response);
    }
}

在需要自定义异常的地方可以直接以如下形式抛出：

throw new BusinessException(503, "异常测试");

可以将错误码、错误信息统一管理成常量，总之，还有优化的空间～

使用上述方式，对filter里抛出的异常捕获不到，所以需要额外处理，如下所示：

@Component
@Slf4j
public class RequestFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        String path = ((HttpServletRequest) servletRequest).getRequestURI();
        if (path.contains("/exception")) {
            throw new BusinessException(401, "filter内部抛出异常");
        }
        filterChain.doFilter(servletRequest, servletResponse);
    }

}

如上代码所示的filter里面抛出异常，是不会转换为BusinessException的，而是直接抛出：

所以我采取了一个比较low的方式：直接向页面response出文字内容（据说可以采用Order改变类的执行顺序，进行异常捕获，但我还没尝试过）：

  @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        String path = ((HttpServletRequest) servletRequest).getRequestURI();
        try {
            if (path.contains("/exception")) {
                throw new BusinessException(401, "filter内部抛出异常");
            }
            filterChain.doFilter(servletRequest, servletResponse);
            return;
        } catch (Exception e) {
            log.error(e.getMessage());
            ResultResponse response = new ResultResponse();

            if (e instanceof BusinessException) {
                BusinessException be = (BusinessException) e;
                response.setRetCode(be.getCode());
                response.setRetMsg(be.getMessage());
            } else {
                response.setRetCode(500);
                response.setRetMsg(e.getMessage());
            }
            servletResponse.setCharacterEncoding("utf-8");
            servletResponse.getWriter().print(JSONObject.toJSON(response));
            return;

        }
    }