2017.12.21 异常处理和Response(@ControllerAdvice)

一、@ControllerAdvice注解
把@ControllerAdvice注解内部使用@ExceptionHandler、@InitBinder、@ModelAttribute注解的方法应用到所有的 @RequestMapping注解的方法。

如果方法抛出异常，BizExceptionHandler找到匹配的入参，调用方法，把信息写入Response对象，返回。
如果正常返回数据，ResponseHandler经过判断，把信息写入Response对象，返回。

二、Response类
将返回值写入Response类返回。

@Data
public class Response {

    private String code;

    private String message;

    private Object data;

    public Response() {
    }

    public Response(String code, String message) {
        this.code = code;
        this.message = message;
    }

    public static Response success(){
        Response response = new Response();
        response.code = "0";
        response.setMessage("请求成功");
        return response;
    }

    public static Response success(Object data) {
        Response response = new Response();
        response.setCode("0");
        response.setMessage("请求成功");
        response.setData(data);
        return response;
    }

    public static Response error(String code, String message) {
        Response response = new Response(code, message);
        return response;
    }

}

三、异常处理
1.异常处理类(BizExceptionHandler)
用@ControllerAdvice注解注释这个异常处理类。

@ControllerAdvice
public class BizExceptionHandler {

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

    @ExceptionHandler(Exception.class)  
    @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
    @ResponseBody
    public Response all(Exception e) {
        logger.error("Exception:", e);
        return Response.error("10000", "未知错误，请联系相关管理人员");
    }

    @ExceptionHandler(BizRuntimeException.class)   //入参，定义的异常类型
    @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR) //返回的http状态码
    @ResponseBody
    public Response bizException(BizRuntimeException e) {
        logger.warn("请求数据抛出逻辑异常：{}", e.getMessage());
        return Response.error(e.getCode(), e.getMessage());
    }
}

@ResponseStatus注解是修饰类的
它有两个属性，value属性是http状态码，比如404，500等。reason是错误信息
如：@ResponseStatus(value=HttpStatus.FORBIDDEN,reason=”用户不匹配”)

2.自定义异常类和常数类(异常Code和描述)
①自定义异常类(可以定义多个，通过Handler中不同入参区分)

public class BizRuntimeException extends RuntimeException  {

    private String code;

    private String message;

    public BizRuntimeException(String code) {
        super(ExceptionConstant.getMessage(code));
        this.code = code;
        this.message = ExceptionConstant.getMessage(code);
    }

    public String getCode() {
        return code;
    }

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

    @Override
    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

②常数类

public abstract class ExceptionConstant {
    private static Map message = new HashMap();

    public static final String ACCOUNT_EXISTED = "5000";
    public static final String PASSWORD_ERROR = "5001";

    static {
        message.put(ACCOUNT_EXISTED, "账号已存在");
        message.put(PASSWORD_ERROR,"密码错误");
    }

    public static String getMessage(String code) {
        return message.get(code);
    }
}

③使用时：

throw new BizRuntimeException(ExceptionConstant.ACCOUNT_EXISTED);

四、ResponseHandler
1.ResponseHandler返回值处理类

@ControllerAdvice
public class ResponseHandler implements ResponseBodyAdvice