3-global exception handling

exception handling (SpringMVC knowledge )

Understanding anomalies

SpringMVC Annotation processing

The processing method is When the core controller is loaded , Therefore, exceptions in parameters can be intercepted

import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

@Component
// Develop exception handlers using annotations 
// Declare that the class is a Controller Notification class of , Once declared, the class is loaded as an exception handler 
// Can be in controller Enhance the function before and after 
@ControllerAdvice
public class ExceptionAdvice {
    

    // The methods defined in the class carry @ExceptionHandler Annotated are treated as exception handlers , Add the exception type actually handled later 
    @ExceptionHandler(NullPointerException.class)
    @ResponseBody
    public String doNullException(Exception ex){
    
        return " Null pointer exception ";
    }

    @ExceptionHandler(ArithmeticException.class)
    @ResponseBody
    public String doArithmeticException(Exception ex){
    
        return "ArithmeticException";
    }

    @ExceptionHandler(Exception.class)
    @ResponseBody
    public String doException(Exception ex){
    
        return "all";
    }
}

Project exception handling scheme 【 understand 】

Custom exception

Business exceptions ( user ) BusinessException

// Custom exception inheritance RuntimeException, Covering all constructors of the parent class 
public class BusinessException extends RuntimeException {
    
    public BusinessException() {
    
    }

    public BusinessException(String message) {
    
        super(message);
    }

    public BusinessException(String message, Throwable cause) {
    
        super(message, cause);
    }

    public BusinessException(Throwable cause) {
    
        super(cause);
    }

    public BusinessException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
    
        super(message, cause, enableSuppression, writableStackTrace);
    }
}

System exception ： SystemException

// Custom exception inheritance RuntimeException, Covering all constructors of the parent class 
public class SystemException extends RuntimeException {
    
    public SystemException() {
    
    }

    public SystemException(String message) {
    
        super(message);
    }

    public SystemException(String message, Throwable cause) {
    
        super(message, cause);
    }

    public SystemException(Throwable cause) {
    
        super(cause);
    }

    public SystemException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
    
        super(message, cause, enableSuppression, writableStackTrace);
    }
}

Other anomalies : DevelopException

// Custom exception inheritance RuntimeException, Covering all constructors of the parent class 
public class DevelopException extends RuntimeException {
    
    public DevelopException() {
    
    }

    public DevelopException(String message) {
    
        super(message);
    }

    public DevelopException(String message, Throwable cause) {
    
        super(message, cause);
    }

    public DevelopException(Throwable cause) {
    
        super(cause);
    }

    public DevelopException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
    
        super(message, cause, enableSuppression, writableStackTrace);
    }
}

The custom exception is wrapped as an exception

public void save(){
    
    // If an exception occurs in the business layer , The code with exception is try...catch... Handle 
    // stay catch Wrap the exception that appears into a custom exception , At the same time, be sure to pass the current exception object into the custom exception , Avoid the disappearance of real exception information 
    try {
    
        throw new SQLException();
    } catch (SQLException e) {
    
        throw new SystemException(" Database connection timeout ！",e);
    }
}

Unified handling of exceptions

import org.springframework.stereotype.Component;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

@Component
@ControllerAdvice
public class ProjectExceptionAdvice {
    

    @ExceptionHandler(BusinessException.class)
    @ResponseBody()
    public String doBusinessException(Exception ex, Model m){
    
        // Using parameter Model Transfer the data to be saved to the page , Function equivalent to ModelAndView
        // The message of business exception shall be sent to the user for viewing 
// m.addAttribute("msg",ex.getMessage());
        return ex.getMessage();
    }

    @ExceptionHandler(value = {
    SystemException.class})
    @ResponseBody
    public String doSystemException(Exception ex, Model m){
    
        // Do not send the message of system exception to the user for viewing , Send unified information to users 
// m.addAttribute("msg"," Server problem , Please contact the Administrator ！");
        // The actual problem phenomenon should be transmitted to redis The server , The operation and maintenance personnel can view through the background system 
        // The actual problems should be passed on to redis The server , The operation and maintenance personnel can view through the background system 
        return " Server problem , Please contact the Administrator ！";
    }

    @ExceptionHandler(Exception.class)
    @ResponseBody
    public String doException(Exception ex, Model m){
    
// m.addAttribute("msg",ex.getMessage());
        // take ex Save the object 
        return ex.getMessage();
    }

}

Unified exception handling

@Component
@ControllerAdvice
@Log4j2
public class ProjectExceptionAdvice {
    

    @ExceptionHandler(BusinessException.class)
    @ResponseBody()
    public ResponseResult doBusinessException(Exception exception, Model m){
    
        // Using parameter Model Transfer the data to be saved to the page , Function equivalent to ModelAndView
        // The message of business exception shall be sent to the user for viewing 
// m.addAttribute("msg",ex.getMessage());
// return ex.getMessage();
        log.error("catch exception:{}", exception.getMessage());
        return ResponseResult.errorResult(500,exception.getMessage());
    }

    @ExceptionHandler(value = {
    SystemException.class})
    @ResponseBody
    public ResponseResult doSystemException(Exception exception, Model m){
    
        // Do not send the message of system exception to the user for viewing , Send unified information to users 
// m.addAttribute("msg"," Server problem , Please contact the Administrator ！");
        // The actual problem phenomenon should be transmitted to redis The server , The operation and maintenance personnel can view through the background system 
        // The actual problems should be passed on to redis The server , The operation and maintenance personnel can view through the background system 
// return " Server problem , Please contact the Administrator ！";
        log.error("catch exception:{}", exception.getMessage());
        return ResponseResult.errorResult(503," Server problem , Please contact the Administrator ！");
    }

    @ExceptionHandler(Exception.class)
    @ResponseBody
    public ResponseResult doException(Exception exception, Model m){
    
// m.addAttribute("msg",ex.getMessage());
        // take ex Save the object 
        // Log 
        exception.printStackTrace();
        log.error("catch exception:{}", exception.getMessage());
        return ResponseResult.errorResultMessage(AppHttpCodeEnum.SERVER_ERROR,exception.getMessage());
    }
}