How to handle exceptions and errors in Spring Boot applications

When developing Spring Boot applications, you will inevitably encounter various exceptions and errors, such as database connection exceptions, code logic errors, user permission exceptions, network connection disconnections, etc. These exceptions and errors have a great impact on the stability and reliability of the application, so we need to handle these exceptions in a timely manner to ensure that the application can continue to run.

This article will introduce how to handle exceptions and errors in Spring Boot applications, including exception capture, error debugging and resolution, exception logging, etc. The following is the specific content:

Exception catching and handling

1. try-catch statement

Add try-catch statement to the code to capture the program Exception during operation. When an exception occurs in the program, it will enter the catch statement block. You can add logic in this block to handle the exception, such as printing the exception information to the log or returning it to the front-end user.

Sample code:

try {
    // 可能发生异常的代码块
} catch (Exception e) {
    // 异常处理逻辑
}

2. @ControllerAdvice annotation

@ControllerAdvice is an annotation provided by the Spring framework to globally handle exceptions in Spring MVC . Through this annotation, we can define global exception handling logic and handle all exceptions uniformly.

Sample code:

@ControllerAdvice
public class GlobalExceptionHandler {
 
    @ExceptionHandler(value = Exception.class)
    public ResponseEntity<Object> handleException(Exception e) {
        // 异常处理逻辑
        return new ResponseEntity<>(e.getMessage(), HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

In the above code, the handleException method can handle all Exception exceptions and return a ResponseEntity object with error information and HTTP status code. In the application, when any Exception exception occurs, this method will be called for exception handling.

3. Custom exception class

When handling exceptions, we can also customize exception classes to represent specific types of exceptions. By customizing exception classes, we can throw exception objects in the program to make the program clearer and easier to understand. At the same time, we can also perform targeted exception handling in the global exception handler.

Sample code:

// 自定义异常类
public class MyException extends Exception {
 
    public MyException(String message) {
        super(message);
    }
}

// 抛出自定义异常
if (someCondition) {
    throw new MyException("发生了 MyException 异常");
}

// 异常处理逻辑
@ControllerAdvice
public class GlobalExceptionHandler {
 
    @ExceptionHandler(value = MyException.class)
    public ResponseEntity<Object> handleMyException(MyException e) {
        // 自定义异常处理逻辑
        return new ResponseEntity<>(e.getMessage(), HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

In the above code, we define a MyException exception class, which will be thrown when the program meets certain conditions. In the global exception handler, we use the @ExceptionHandler(value = MyException.class) annotation to indicate that the method can handle exceptions of the MyException type.

Error debugging and resolution

1. Debug mode debugging

Debugging is the key to solving application errors. By debugging a program, we can view information such as program status, variable values, and execution paths to find the cause of errors. In a Spring Boot application, we can debug by setting the log level to DEBUG.

Add the following code in the application.properties file:

logging.level.root=DEBUG

In the above code, set the log level root to DEBUG. When running the program, the program log will output more debugging information.

2. Logging

Logging error logs is an effective means of finding errors. The Spring Boot application comes with a logging framework - logback, through which we can record error logs. In the logback.xml file, we can configure the log output format, log file storage path, etc.

Sample code:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <appender name="fileAppender" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>logs/springbootdemo.log</file>
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n</pattern>
        </encoder>
        <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
            <fileNamePattern>logs/springbootdemo.%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <maxFileSize>10MB</maxFileSize>
            <maxHistory>30</maxHistory>
            <totalSizeCap>10GB</totalSizeCap>
        </rollingPolicy>
    </appender>
 
    <logger name="com.yourpackage" level="INFO"/>
 
    <root level="INFO">
        <appender-ref ref="fileAppender"/>
    </root>
</configuration>

In the above code, we added an appender named fileAppender to output the log to the specified file. Among them, rollingPolicy is used to configure the file rolling policy, maxFileSize sets the size of a single log file, maxHistory sets the number of days for log file storage, and totalSizeCap sets the total size of log files.

Conclusion

In Spring Boot applications, exception and error handling are a very important part. Through proper exception catching and handling, debugging skills and logging, we can ensure the stability and reliability of the program, thereby providing users with better services.

The above are some basic tips and methods on how to deal with exceptions and errors in Spring Boot applications. I hope it will be helpful to everyone.

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