无涯教程-Spring Boot - 拦截器您可以在以下情况下使用Spring Boot中的拦截器(Intercept

您可以在以下情况下使用Spring Boot中的拦截器(Interceptor)来执行操作-

在将请求发送到控制器之前
在将响应发送给客户端之前

例如，您可以使用拦截器在将请求发送到控制器之前添加请求标头，并在将响应发送到客户端之前添加响应标头。

要使用拦截器，您需要创建支持它的 @Component 类，并且该类应实现 HandlerInterceptor 接口。

以下是使用拦截器时应了解的三种方法-

preHandle() - 用于在将请求发送到控制器之前执行操作，需要返回true。
postHandle() - 用于在将响应发送到客户端之前执行操作。
afterCompletion() - 用于完成请求和响应后执行操作。

观察以下代码以更好地理解-

@Component
public class ProductServiceInterceptor implements HandlerInterceptor {
   @Override
   public boolean preHandle(
      HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
  </span><span class="kwd">return</span><span class="pln"> </span><span class="kwd">true</span><span class="pun">;</span><span class="pln">

}
@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 {}
}

您将必须使用 WebMvcConfigurerAdapter 向 InterceptorRegistry 注册此拦截器，如下所示-

@Component
public class ProductServiceInterceptorAppConfig extends WebMvcConfigurerAdapter {
   @Autowired
   ProductServiceInterceptor productServiceInterceptor;
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(productServiceInterceptor);
}
}

在下面给出的示例中，无涯教程将使用GET产品API，该产品的输出如下-

下面给出了Interceptor类ProductServiceInterceptor.java的代码-

package com.learnfk.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 {
  </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="str">"Pre Handle method is Calling"</span><span class="pun">);</span><span class="pln">
  </span><span class="kwd">return</span><span class="pln"> </span><span class="kwd">true</span><span class="pun">;</span><span class="pln">

}
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response,
Object handler, ModelAndView modelAndView) throws Exception {
  </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="str">"Post Handle method is Calling"</span><span class="pun">);</span><span class="pln">

}
@Override
public void afterCompletion
(HttpServletRequest request, HttpServletResponse response, Object
handler, Exception exception) throws Exception {
  </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="str">"Request and Response is completed"</span><span class="pun">);</span><span class="pln">

}
}

下面提供了用于将拦截器注册到拦截器注册表中的Application Configuration类文件的代码– ProductServiceInterceptorAppConfig.java-

package com.learnfk.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);
}
}

控制器类文件ProductServiceController.java的代码如下所示-

package com.learnfk.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.learnfk.demo.exception.ProductNotfoundException;
import com.learnfk.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);
}
}

下面给出了Product.java的POJO类的代码-

package com.learnfk.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;
}
}

下面给出了主要的Spring Boot应用程序类文件 DemoApplication.java 的代码-

package com.learnfk.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构建的代码- pom.xml 显示在此处-

<?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.learnfk</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>
  </span><span class="tag">&lt;dependency&gt;</span><span class="pln">
     </span><span class="tag">&lt;groupId&gt;</span><span class="pln">org.springframework.boot</span><span class="tag">&lt;/groupId&gt;</span><span class="pln">
     </span><span class="tag">&lt;artifactId&gt;</span><span class="pln">spring-boot-starter-test</span><span class="tag">&lt;/artifactId&gt;</span><span class="pln">
     </span><span class="tag">&lt;scope&gt;</span><span class="pln">test</span><span class="tag">&lt;/scope&gt;</span><span class="pln">
  </span><span class="tag">&lt;/dependency&gt;</span><span class="pln">

</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

这里显示了Gradle Build build.gradle 的代码-

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.learnfk
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)
}

您可以创建可执行的JAR文件，并使用以下Maven或Gradle命令运行Spring Boot应用程序。

对于Maven，使用如下所示的命令-

mvn clean install

在" BUILD SUCCESS"之后，您可以在目标目录下找到JAR文件。

对于Gradle，请使用如下所示的命令-

gradle clean build

在" BUILD SUCCESSFUL"之后，您可以在build/libs目录下找到JAR文件。

您可以使用以下命令运行JAR文件-

java –jar <JARFILE>

现在，应用程序已在Tomcat端口8080上启动，如下所示-

现在在POSTMAN应用程序中点击以下URL，您可以看到输出，如下所示-

GET API: http:// localhost:8080/products

在控制台窗口中，您可以看到Interceptor中添加的System.out.println语句，如下面所示-

无涯教程-Spring Boot - 拦截器

参考链接