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Create Java全局异常捕获处理 .md
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‎Java/Java全局异常捕获处理 .md

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为了项目的正常运行中,异常捕获,记录也是非常重要的，方便我们排查问题，定位问题
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# 定义异常
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为了方便定位异常，自定义了几种异常类，方便我们快速定位异常。
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## 基类
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```java
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public class HttpException extends RuntimeException {
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protected String code;
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protected Integer httpStatusCode = 500;
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}
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```
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## ParameterException
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```java
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public class ParameterException extends HttpException {
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public ParameterException(String code){
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this.code = code;
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this.httpStatusCode = 400;
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}
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}
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```
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## ServerErrorException
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```java
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public class ServerErrorException extends HttpException {
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public ServerErrorException(String code) {
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this.code = code;
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this.httpStatusCode = 500;
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}
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}
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```
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## UnAuthenticatedException
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```java
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public class UnAuthenticatedException extends HttpException{
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public UnAuthenticatedException(String code){
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this.code = code;
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this.httpStatusCode = 401;
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}
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}
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```
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## ForbiddenException
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```java
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public class ForbiddenException extends HttpException {
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public ForbiddenException(String code) {
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this.code = code;
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this.httpStatusCode = 403;
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}
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}
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```
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## NotFoundException
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```java
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public class NotFoundException extends HttpException {
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public NotFoundException(String code){
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this.httpStatusCode = 404;
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this.code = code;
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}
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}
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```
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这里定义了我在项目中常用的几种异常，也可根据实际情况定义自己所需的异常。
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# 捕获异常
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捕获异常需要用到一个注解`@ControllerAdvice`,关于它的详细解释可查看[文档](https://docs.spring.io/spring-framework/docs/5.0.0.M1/javadoc-api/org/springframework/web/bind/annotation/ControllerAdvice.html)。
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使用方法如下，定义一个异常捕获类
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```java
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@ControllerAdvice
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public class GlobalExceptionAdvice {
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}
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```
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这个类就已经实现了捕获全局异常的功能，下面在加上上面定义的几种异常
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```java
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@ControllerAdvice
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public class GlobalExceptionAdvice {
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@ExceptionHandler(UnAuthenticatedException.class)
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public ResponseEntity unAuthenticatedException(UnAuthenticatedException e) {
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return ResponseEntity.status(HttpStatus.UNAUTHORIZED).body(e.getCode());
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}
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@ExceptionHandler(ParameterException.class)
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public ResponseEntity handleParameterException(ParameterException e) {
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return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(e.getCode());
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}
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@ExceptionHandler(ForbiddenException.class)
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public ResponseEntity handleForbiddenException(ForbiddenException e) {
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return ResponseEntity.status(HttpStatus.FORBIDDEN).body(e.getCode());
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}
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@ExceptionHandler(NotFoundException.class)
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public ResponseEntity handleNotFoundException(NotFoundException e) {
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return ResponseEntity.status(HttpStatus.NOT_FOUND).body(e.getCode());
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}
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@ExceptionHandler(RuntimeException.class)
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public ResponseEntity handleRunTimeException(RuntimeException e) {
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return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(500);
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}
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}
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```
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`@ExceptionHandler`注解表示该方法捕获的异常类型，就可以在不同的异常中进行不同的处理方式。
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# 记录异常
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捕获到异常之后我们要记录下来，方便我们对bug的追踪解决。
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记录方法有多种多样的，比如记录到数据库或者`log`文件中。我使用了第二种方式。
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## 加入依赖
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```xml
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<dependency>
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<groupId>org.projectlombok</groupId>
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<artifactId>lombok</artifactId>
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<optional>true</optional>
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</dependency>
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<dependency>
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<groupId>commons-logging</groupId>
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<artifactId>commons-logging</artifactId>
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<version>1.2</version>
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</dependency>
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<dependency>
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<groupId>org.apache.logging.log4j</groupId>
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<artifactId>log4j-api</artifactId>
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<version>2.2</version>
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</dependency>
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<dependency>
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<groupId>org.apache.logging.log4j</groupId>
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<artifactId>log4j-core</artifactId>
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<version>2.2</version>
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</dependency>
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<dependency>
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<groupId>org.apache.logging.log4j</groupId>
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<artifactId>log4j-jcl</artifactId>
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<version>2.2</version>
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</dependency>
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```
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## 增加日志配置文件
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`logback.xml`
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<configuration>
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<!-- 控制台 appender, 几乎是默认的配置 -->
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<appender name="stdout" class="ch.qos.logback.core.ConsoleAppender">
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<encoder charset="UTF-8">
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<!-- 输出的日志文本格式, 其他的 appender 与之相同 -->
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<pattern> %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} %L - %msg%n</pattern>
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<charset>UTF-8</charset>
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</encoder>
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</appender>
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<!-- info 级别的 appender -->
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<appender name="info" class="ch.qos.logback.core.rolling.RollingFileAppender">
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<!-- 日志写入的文件名, 可以是相对目录, 也可以是绝对目录, 如果上级目录不存在会自动创建 -->
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<file>./logs/info/log-stack.log</file>
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<!-- 如果是 true, 日志被追加到文件结尾; 如果是 false, 清空现存文件. 默认是true -->
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<append>true</append>
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<!-- 日志级别过滤器, 只打 INFO 级别的日志-->
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<filter class="ch.qos.logback.classic.filter.LevelFilter">
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<level>INFO</level>
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<!-- 下面2个属性表示: 匹配 level 的接受打印, 不匹配的拒绝打印 -->
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<onMatch>ACCEPT</onMatch>
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<onMismatch>DENY</onMismatch>
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</filter>
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<!-- 最常用的滚动策略, 它根据时间来制定滚动策略, 既负责滚动也负责触发滚动 -->
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<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
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<!-- 设置滚动文件规则, 如果直接使用 %d, 默认格式是 yyyy-MM-dd -->
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<fileNamePattern>./logs/info/log-stack.%d{yyyy-MM-dd}.log</fileNamePattern>
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<!-- 保留14天的日志 -->
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<maxHistory>30</maxHistory>
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</rollingPolicy>
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<!-- 定义日志输出格式 -->
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<encoder charset="UTF-8">
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<pattern> %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} %L - %msg%n</pattern>
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<charset>UTF-8</charset>
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</encoder>
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</appender>
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<!-- error 级别的 appender -->
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<appender name="error" class="ch.qos.logback.core.rolling.RollingFileAppender">
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<file>./logs/error/log-stack.log</file>
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<append>true</append>
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<filter class="ch.qos.logback.classic.filter.LevelFilter">
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<level>ERROR</level>
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<onMatch>ACCEPT</onMatch>
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<onMismatch>DENY</onMismatch>
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</filter>
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<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
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<fileNamePattern>./logs/error/log-stack.%d{yyyy-MM-dd}.log</fileNamePattern>
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<!-- 保留7天的日志 -->
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<maxHistory>30</maxHistory>
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</rollingPolicy>
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<!-- 定义日志输出格式 -->
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<encoder charset="UTF-8">
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<pattern> %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} %L - %msg%n</pattern>
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<charset>UTF-8</charset>
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</encoder>
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</appender>
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<!-- error 级别的 appender -->
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<appender name="debug" class="ch.qos.logback.core.rolling.RollingFileAppender">
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<file>./logs/debug/log-stack.log</file>
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<append>true</append>
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<filter class="ch.qos.logback.classic.filter.LevelFilter">
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<level>DEBUG</level>
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<onMatch>ACCEPT</onMatch>
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<onMismatch>DENY</onMismatch>
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</filter>
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<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
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<fileNamePattern>./logs/debug/log-stack.%d{yyyy-MM-dd}.log</fileNamePattern>
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<!-- 保留7天的日志 -->
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<maxHistory>30</maxHistory>
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</rollingPolicy>
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<!-- 定义日志输出格式 -->
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<encoder charset="UTF-8">
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<pattern> %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} %L - %msg%n</pattern>
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<charset>UTF-8</charset>
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</encoder>
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</appender>
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<!-- 指定 com.github 下的日志打印级别, appender -->
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<logger name="com.github" level="debug" additivity="false">
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<appender-ref ref="stdout"/>
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<appender-ref ref="info"/>
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<appender-ref ref="error"/>
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<appender-ref ref="debug"/>
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</logger>
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<root level="info">
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<appender-ref ref="stdout"/>
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<appender-ref ref="info"/>
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<appender-ref ref="error"/>
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</root>
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</configuration>
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```
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## 写入日志
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```java
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@ControllerAdvice
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@Slf4j
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public class GlobalExceptionAdvice {
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@ExceptionHandler(ParameterException.class)
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public ResponseEntity handleParameterException(ParameterException e) {
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log.error(e.getLocalizedMessage());
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return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(e.getCode());
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}
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}
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```
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# 完善异常信息
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文章中的异常只定义了`code`，具体的异常信息可以写在配置文件中或者保存在数据库中，在捕获到异常之后，找到对应的描述信息返回调用者，增加友好度。
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# 完善记录日志
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以上如果发生了异常，在日志文件中是这样记录的
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```
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10:19:32.024 [http-nio-8080-exec-2] ERROR c.g.e.d.advice.GlobalExceptionAdvice 41 - / by zero
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```
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发现记录的行号是在`GlobalExceptionAdvice`类中，并非是代码真实的位置。
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如果要记录到代码的真实位置可以这样实现
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```java
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public String getExceptionDetail(Exception e) {
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StringBuilder stringBuilder = new StringBuilder();
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stringBuilder.append(e.getClass() + System.getProperty("line.separator"));
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stringBuilder.append(e.getLocalizedMessage() + System.getProperty("line.separator"));
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StackTraceElement[] arr = e.getStackTrace();
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for (int i = 0; i < arr.length; i++) {
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stringBuilder.append(arr[i].toString() + System.getProperty("line.separator"));
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}
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return stringBuilder.toString();
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}
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```
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```java
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log.error(getExceptionDetail(e));
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```
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根据实际情况选择适合自己的方式
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# 完整代码
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[Github](https://github.com/lizeze/exception-demo)
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[Gitee](https://gitee.com/zeze.li/exception-demo)

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