Spring Boot異常處理

處理API中的異常和錯誤並向客戶端發送適當的響應對企業應用程序有利。在本章中,將學習如何在Spring Boot中處理異常。

在繼續進行異常處理之前,瞭解以下註解。

控制器Advice

[@ControllerAdvice](https://github.com/ControllerAdvice "@ControllerAdvice")是一個註解,用於全局處理異常。

異常處理程序

[@ExceptionHandler](https://github.com/ExceptionHandler "@ExceptionHandler")是一個註釋,用於處理特定異常並將自定義響應發送到客戶端。使用以下代碼創建[@ControllerAdvice](https://github.com/ControllerAdvice "@ControllerAdvice")類來全局處理異常 -

package com.yiibai.demo.exception;

import org.springframework.web.bind.annotation.ControllerAdvice;

@ControllerAdvice
   public class ProductExceptionController {
}

定義一個擴展RuntimeException類的子類。

package com.yiibai.demo.exception;

public class ProductNotfoundException extends RuntimeException {
   private static final long serialVersionUID = 1L;
}

可以定義[@ExceptionHandler](https://github.com/ExceptionHandler "@ExceptionHandler")方法來處理異常,如圖所示。 此方法應用於編寫Controller Advice類文件。

@ExceptionHandler(value = ProductNotfoundException.class)

public ResponseEntity<Object> exception(ProductNotfoundException exception) {
}

現在,使用下面給出的代碼從API中拋出異常。

@RequestMapping(value = "/products/{id}", method = RequestMethod.PUT)
public ResponseEntity<Object> updateProduct() { 
   throw new ProductNotfoundException();
}

下面給出了處理異常的完整代碼。在此示例中,使用PUT API更新產品。 此處,在更新產品時,如果找不到產品,則將響應錯誤消息返回爲:"ProductNotFoundException"。 請注意,ProductNotFoundException異常類應該擴展RuntimeException

package com.yiibai.demo.exception;
public class ProductNotfoundException extends RuntimeException {
   private static final long serialVersionUID = 1L;
}

下面給出了用於全局處理異常的ControllerAdvice類。在這個類文件中定義任何異常處理方法。

package com.yiibai.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;

@ControllerAdvice
public class ProductExceptionController {
   @ExceptionHandler(value = ProductNotfoundException.class)
   public ResponseEntity<Object> exception(ProductNotfoundException exception) {
      return new ResponseEntity<>("Product not found", HttpStatus.NOT_FOUND);
   }
}

下面給出了Product Service API控制器文件以更新產品。 如果找不到產品,則拋出ProductNotFoundException類。

package com.yiibai.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.yiibai.demo.exception.ProductNotfoundException;
import com.yiibai.demo.model.Product;

@RestController
public 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);
   }
}

Spring Boot應用程序主類文件的代碼如下 -

package com.yiibai.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {
   public static void main(String[] args) {
      SpringApplication.run(DemoApplication.class, args);
   }
}

產品POJO類的代碼如下 -

package com.yiibai.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的代碼 - 文件:pom.xml 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.yiibai</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構建文件:build.gradle 的代碼如下 -

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.yiibai'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8

repositories {
   mavenCentral()
}
dependencies {
   compile('org.springframework.boot:spring-boot-starter-web')
   testCompile('org.springframework.boot:spring-boot-starter-test')
}

創建可執行的JAR文件,並使用Maven或Gradle命令運行Spring Boot應用程序,對於Maven,可以使用以下命令 -

mvn clean install

在控制檯看到有"BUILD SUCCESS"之後,在目標目錄下找到JAR文件。對於Gradle,使用以下命令 -

gradle clean build

在控制檯看到有"BUILD SUCCESS"之後,在build/libs目錄下找到JAR文件。使用以下命令運行JAR文件 -

java –jar <JARFILE>

這將在Tomcat端口8080上啓動應用程序,如下所示 -

Spring

現在點擊 POSTMAN 應用程序中的URL,更新URL爲 : http://localhost:8080/products/3 , 可以看到如下輸出 -

Spring