您可以在 Spring Boot 中使用 Interceptor 在以下情況下執(zhí)行操作 

在向控制器發(fā)送請(qǐng)求之前

在向客戶端發(fā)送響應(yīng)之前

例如，您可以使用攔截器在向控制器發(fā)送請(qǐng)求之前添加請(qǐng)求頭，并在向客戶端發(fā)送響應(yīng)之前添加響應(yīng)頭。

要使用攔截器，您需要?jiǎng)?chuàng)建支持它的@Component類，并且它應(yīng)該實(shí)現(xiàn)HandlerInterceptor接口。

以下是您在使用攔截器時(shí)應(yīng)該了解的三種方法 

preHandle()方法 - 用于在將請(qǐng)求發(fā)送到控制器之前執(zhí)行操作。此方法應(yīng)返回 true 以將響應(yīng)返回給客戶端。

postHandle()方法 - 用于在向客戶端發(fā)送響應(yīng)之前執(zhí)行操作。

afterCompletion()方法 - 用于在完成請(qǐng)求和響應(yīng)后執(zhí)行操作。

觀察以下代碼以更好地理解 

@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 {}
}

您必須使用WebMvcConfigurerAdapter向InterceptorRegistry注冊(cè)此攔截器，如下所示

@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，我們將點(diǎn)擊 GET products API，它提供如下所示的輸出 

攔截器類 ProductServiceInterceptor.java 的代碼如下

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");
   }
}

下面給出了將攔截器注冊(cè)到攔截器注冊(cè)表的應(yīng)用程序配置類文件的代碼

 ProductServiceInterceptorAppConfig.java

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);
   }
}

控制器類文件 ProductServiceController.java 的代碼如下

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);
   }
}

Product.java 的 POJO 類代碼如下

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)用程序類文件DemoApplication.java的代碼如下

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 構(gòu)建的代碼 - pom.xml顯示在這里

<?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的代碼如下所示

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')
}

您可以創(chuàng)建一個(gè)可執(zhí)行 JAR 文件，并使用以下 Maven 或 Gradle 命令運(yùn)行 Spring Boot 應(yīng)用程序。

對(duì)于 Maven，使用如下所示的命令

mvn clean install

“BUILD SUCCESS”后，可以在目標(biāo)目錄下找到JAR文件。

對(duì)于 Gradle，使用如下所示的命令

gradle clean build

“BUILD SUCCESSFUL”后，可以在build/libs目錄下找到JAR文件。

您可以使用以下命令運(yùn)行 JAR 文件

java –jar <JARFILE> 

現(xiàn)在，應(yīng)用程序已在 Tomcat 端口 8080 上啟動(dòng)，如下所示

現(xiàn)在在 POSTMAN 應(yīng)用程序中點(diǎn)擊以下 URL，您可以看到如下所示的輸出 

獲取 API：http://localhost:8080/products

在控制臺(tái)窗口中，您可以看到在攔截器中添加的 System.out.println 語(yǔ)句，如下面的屏幕截圖所示

以上就是關(guān)于“SpringBoot攔截器詳解”的介紹，想了解更多相關(guān)知識(shí)，不妨來(lái)關(guān)注一下動(dòng)力節(jié)點(diǎn)的SpringBoot教程，可以免費(fèi)在線學(xué)習(xí)，對(duì)大家的學(xué)習(xí)會(huì)有很大幫助哦。