Spring Boot快速入門之（十三）： 攔截器
【注】本文譯自： https://www.tutorialspoint.com/spring_boot/spring_boot_interceptor.htm
? ? ? ? 在以下兩種情況下，可以在?Spring Boot 中使用攔截器來執(zhí)行操作：
發(fā)送請(qǐng)求到控制器之前
發(fā)送響應(yīng)到客戶端之前
? ? ? ?譬如，可以使用攔截器在發(fā)送請(qǐng)求到控制器之前添加請(qǐng)求頭，并在發(fā)送響應(yīng)到客戶端之前添加響應(yīng)頭。
? ? ? ?要用攔截器，你需要?jiǎng)?chuàng)建?@Component?類，并且要實(shí)現(xiàn)?HandlerInterceptor?接口。
? ? ? ?下面是使用攔截器要知道的三個(gè)方法：
preHandle()?方法：用于在發(fā)送請(qǐng)求到控制器之前執(zhí)行操作。這個(gè)方法應(yīng)當(dāng)返回 true 以響應(yīng)客戶端。
postHandle()?方法：用于在發(fā)送響應(yīng)到客戶端之前執(zhí)行操作。
afterCompletion()?方法： 用于在請(qǐng)求和響應(yīng)完成之后執(zhí)行操作。
? ? ? ?觀察以下代碼以加深理解：
@Component
public class ProductServiceInterceptor implements HandlerInterceptor {
???@Override
???public boolean preHandle(
??????HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
??????
??????return true;
???}
???@Override
???public void postHandle(
??????HttpServletRequest request, HttpServletResponse response, Object handler,
??????ModelAndView modelAndView) throws Exception {}
???
???@Override
???public void afterCompletion(HttpServletRequest request, HttpServletResponse response,
??????Object handler, Exception exception) throws Exception {}
}
? ? ? ?還要通過?WebMvcConfigurerAdapter?用?InterceptorRegistry?注冊(cè)這個(gè)攔截器：
@Component
public class ProductServiceInterceptorAppConfig extends WebMvcConfigurerAdapter {
???@Autowired
???ProductServiceInterceptor productServiceInterceptor;
???@Override
???public void addInterceptors(InterceptorRegistry registry) {
??????registry.addInterceptor(productServiceInterceptor);
???}
}
? ? ? ?在下面給出的示例中，我們將要使用后面給出的?GET products API：
? ? ? ?Interceptor 類文件 ProductServiceInterceptor.java 如下所示：
package com.tutorialspoint.demo.interceptor;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
@Component
public class ProductServiceInterceptor implements HandlerInterceptor {
???@Override
???public boolean preHandle
??????(HttpServletRequest request, HttpServletResponse response, Object handler)
??????throws Exception {
??????
??????System.out.println("Pre Handle method is Calling");
??????return true;
???}
???@Override
???public void postHandle(HttpServletRequest request, HttpServletResponse response,
??????Object handler, ModelAndView modelAndView) throws Exception {
??????
??????System.out.println("Post Handle method is Calling");
???}
???@Override
???public void afterCompletion
??????(HttpServletRequest request, HttpServletResponse response, Object
??????handler, Exception exception) throws Exception {
??????
??????System.out.println("Request and Response is completed");
???}
}
? ? ? ? Application Configuration 類文件把攔截器注冊(cè)到 Interceptor Registry中，ProductServiceInterceptorAppConfig.java 文件如下：
package com.tutorialspoint.demo.interceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
@Component
public class ProductServiceInterceptorAppConfig extends WebMvcConfigurerAdapter {
???@Autowired
???ProductServiceInterceptor productServiceInterceptor;
???@Override
???public void addInterceptors(InterceptorRegistry registry) {
??????registry.addInterceptor(productServiceInterceptor);
???}
}
? ? ? Controller 類文件 ProductServiceController.java 如下：
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;
@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")
???public ResponseEntity<Object> getProduct() {
??????return new ResponseEntity<>(productRepo.values(), HttpStatus.OK);
???}
}
? ? ? ?POJO 類文件 Product.java 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;
???}
}
? ? ? ?主?Spring Boot 應(yīng)用類文件?DemoApplication.java?如下所示：
package com.tutorialspoint.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);???
???}
}
? ? ? ?Maven build –?pom.xml?文件在此：
<?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?文件在此：
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 = 1.8
repositories {
???mavenCentral()
}
dependencies {
???compile('org.springframework.boot:spring-boot-starter-web')
???testCompile('org.springframework.boot:spring-boot-starter-test')
}
? ? ? 你可以使用下面的 Maven 或 Gradle 命令創(chuàng)建可執(zhí)行的?JAR 文件，運(yùn)行 Spring Boot 應(yīng)用：
? ? ? ?對(duì)于 Maven，使用以下命令：
mvn clean install
? ? ? ?在 “BUILD SUCCESS” 之后，你可以在 target 目錄下找到 JAR 文件：
? ? ? 對(duì)于?Gradle，使用以下命令：
gradle clean build
? ? ? ?在 “BUILD SUCCESSFUL” 之后，你可以在 build/libs 目錄下找到?JAR 文件：
? ? ? ?可以使用以下命令運(yùn)行 JAR 文件：
java –jar <JARFILE>
? ? ? ?此時(shí)，應(yīng)用已經(jīng)在 Tomcat 8080?端口啟動(dòng)了，如下所示：
? ? ? ?在?POSTMAN 應(yīng)用中單擊以下?URL，你可以看到下面的結(jié)果：
GET API:?http://localhost:8080/products
? ? ? ?在控制臺(tái)窗口，你可以看到加在攔截器中的?System.out.println 打印出來的結(jié)果，截屏如下：
