【注】本文译自:[https://www.tutorialspoint.com/spring_boot/spring_boot_exception_handling.htm](https://www.tutorialspoint.com/spring_boot/spring_boot_exception_handling.htm)
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对于企业应用而言,在 API 中处理好异常和错误是至关重要的。本文将带你学习如果在 Spring Boot 中处理异常。
在学习异常处理前让我们先来理解下面的注解:
Controller Advice
@ControllerAdvice 注解用于处理全局异常。
Exception Handler
@ExceptionHandler 注解是用于处理指定的异常并向客户端发送一个自定义的响应。
可以使用下面的代码来创建 @ControllerAdvice 类以处理全局异常:
package com.tutorialspoint.demo.exception;import org.springframework.web.bind.annotation.ControllerAdvice;@ControllerAdvice public class ProductExceptionController {}
定义一个继承 RuntimeException 的类。
package com.tutorialspoint.demo.exception;public class ProductNotfoundException extends RuntimeException { private static final long serialVersionUID = 1L;}
如下所示,可以定义 @ExceptionHandler 方法来处理异常。这个方法应当被用于编写 Controller Advice 类文件。
@ExceptionHandler(value = ProductNotfoundException.class)public ResponseEntity<Object> exception(ProductNotfoundException exception) {}
现在,使用以下代码来抛出来自 API 的异常:
@RequestMapping(value = "/products/{id}", method = RequestMethod.PUT)public ResponseEntity<Object> updateProduct() { throw new ProductNotfoundException();}
完整的异常处理代码如下所示。在这个例子中,我们使用 PUT API 来更新产品。当更新产品时,如果找不到产品,返回的响应消息是 “Product not found”。注意 **ProductNotFoundExceptio**n 异常类应当继承 **RuntimeException**。
package com.tutorialspoint.demo.exception;public class ProductNotfoundException extends RuntimeException { private static final long serialVersionUID = 1L;}
Controller Advice 类处理全局异常,如下所示。我们可以在这个类文件中定义任何 Exception Handler 方法。
package com.tutorialspoint.demo.exception;import org.springframework.http.HttpStatus;import org.springframework.http.ResponseEntity;import org.springframework.web.bind.annotation.ControllerAdvice;import org.springframework.web.bind.annotation.ExceptionHandler;@ControllerAdvicepublic class ProductExceptionController { @ExceptionHandler(value = ProductNotfoundException.class) public ResponseEntity<Object> exception(ProductNotfoundException exception) { return new ResponseEntity<>("Product not found", HttpStatus.NOT_FOUND); }}
下面的 Product Service API controller 文件更新产品。如果产品不存在,就抛出 ProductNotFoundException 类。
package com.tutorialspoint.demo.controller;import java.util.HashMap;import java.util.Map;import org.springframework.http.HttpStatus;import org.springframework.http.ResponseEntity;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RequestBody;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;import org.springframework.web.bind.annotation.RestController;import com.tutorialspoint.demo.exception.ProductNotfoundException;import com.tutorialspoint.demo.model.Product;@RestControllerpublic class ProductServiceController { private static Map<String, Product> productRepo = new HashMap<>(); static { Product honey = new Product(); honey.setId("1"); honey.setName("Honey"); productRepo.put(honey.getId(), honey); Product almond = new Product(); almond.setId("2"); almond.setName("Almond"); productRepo.put(almond.getId(), almond); } @RequestMapping(value = "/products/{id}", method = RequestMethod.PUT) public ResponseEntity<Object> updateProduct(@PathVariable("id") String id, @RequestBody Product product) { if(!productRepo.containsKey(id))throw new ProductNotfoundException(); productRepo.remove(id); product.setId(id); productRepo.put(id, product); return new ResponseEntity<>("Product is updated successfully", HttpStatus.OK); }}
**主 Spring Boot 应用类**文件如下:
package com.tutorialspoint.demo;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); }}
**产品 POJO 类** 如下:
package com.tutorialspoint.demo.model;public class Product { private String id; private String name; public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; }}
** Maven build – pom.xml** 代码如下所示:
<?xml version = "1.0" encoding = "UTF-8"?><project xmlns = "http://maven.apache.org/POM/4.0.0" xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation = "http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.tutorialspoint</groupId> <artifactId>demo</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>demo</name> <description>Demo project for Spring Boot</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.5.8.RELEASE</version> <relativePath/> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
Gradle Build – build.gradle 代码如下:
buildscript { ext { springBootVersion = '1.5.8.RELEASE' } repositories { mavenCentral() } dependencies { classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}") }}apply plugin: 'java'apply plugin: 'eclipse'apply plugin: 'org.springframework.boot'group = 'com.tutorialspoint'version = '0.0.1-SNAPSHOT'sourceCompatibility = 1.8repositories { mavenCentral()}dependencies { compile('org.springframework.boot:spring-boot-starter-web') testCompile('org.springframework.boot:spring-boot-starter-test')}
你可以使用 Maven 或 Gradle 命令构建 JAR 并运行 Spring Boot 应用:
Maven 命令如下:
mvn clean install
“BUILD SUCCESS” 之后,你可以在 target 目录下找到 JAR 文件。
Gradle 可以使用如下命令:
gradle clean build
“BUILD SUCCESSFUL” 后,你可以在 build/libs 目录下找到 JAR 文件。
你可以使用下面的命令运行 JAR 文件。
java –jar <JARFILE>
在 Tomcat 8080 端口启动应用,如下所示:
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现在,在 POSTMAN 应用中单击下面的 URL,你可以看到如下输出:
更新 URL: [http://localhost:8080/products/3](http://localhost:8080/products/3)
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