Spring Boot 拦截器



  • 拦截器

    在以下情况下,可以使用Spring Boot中的Interceptor(拦截器)来执行操作:
    • 在将请求发送到控制器之前(拦截请求)
    • 在将响应发送给客户端之前(拦截响应)
    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,并且它应该实现HandlerInterceptor接口。
    以下是使用拦截器时应了解的三种方法-
    • preHandle()方法 - 用于在将请求发送到控制器之前执行操作。此方法应返回true,以将响应返回给客户端。
    • postHandle()方法 - 用于在将响应发送到客户端之前执行操作。
    • afterCompletion()方法 - 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 {
          
          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 {}
    }
    
    
    您将必须使用WebMvcConfigurerAdapterInterceptorRegistry注册此拦截器r,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,我们将使用GET products API,该产品的输出如下 -
    下面给出了Interceptor类ProductServiceInterceptor.java的代码-
    
    package com.jc2182.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.jc2182.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.jc2182.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.jc2182.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.jc2182.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Spring Boot应用程序类文件DemoApplication.java的main方法代码-
    
    package com.jc2182.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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.3.0.BUILD-SNAPSHOT</version>
            <relativePath/> <!-- lookup parent from repository -->
        </parent>
        <groupId>com.jc2182</groupId>
        <artifactId>demo</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>demo</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <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>
                <exclusions>
                    <exclusion>
                        <groupId>org.junit.vintage</groupId>
                        <artifactId>junit-vintage-engine</artifactId>
                    </exclusion>
                </exclusions>
            </dependency>
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    
        <repositories>
            <repository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
            </repository>
            <repository>
                <id>spring-snapshots</id>
                <name>Spring Snapshots</name>
                <url>https://repo.spring.io/snapshot</url>
                <snapshots>
                    <enabled>true</enabled>
                </snapshots>
            </repository>
        </repositories>
        <pluginRepositories>
            <pluginRepository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
            </pluginRepository>
            <pluginRepository>
                <id>spring-snapshots</id>
                <name>Spring Snapshots</name>
                <url>https://repo.spring.io/snapshot</url>
                <snapshots>
                    <enabled>true</enabled>
                </snapshots>
            </pluginRepository>
        </pluginRepositories>
    
    </project>
    
    
    下面给出了Gradle Build – build.gradle的代码-
    
    plugins {
        id 'org.springframework.boot' version '2.3.0.BUILD-SNAPSHOT'
        id 'io.spring.dependency-management' version '1.0.9.RELEASE'
        id 'java'
    }
    
    group = 'com.jc2182'
    version = '0.0.1-SNAPSHOT'
    sourceCompatibility = '1.8'
    
    repositories {
        mavenCentral()
        maven { url 'https://repo.spring.io/milestone' }
        maven { url 'https://repo.spring.io/snapshot' }
    }
    
    dependencies {
        implementation 'org.springframework.boot:spring-boot-starter-web'
        testImplementation('org.springframework.boot:spring-boot-starter-test') {
            exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
        }
    }
    
    test {
        useJUnitPlatform()
    }    
    
    
    RESTFul Web 服务参考>>>
    您可以创建一个可执行的JAR文件,并使用Maven或Gradle命令运行Spring Boot应用程序-
    对于Maven,您可以使用以下命令-
    
    mvn clean install
    
    
    在“BUILD SUCCESS”之后,您可以在target目录下找到JAR文件。
    对于Gradle,您可以使用以下命令-
    
    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>
    
    
    在Tomcat端口8080上启动应用程序
    现在在POSTMAN应用程序中请求URL,您可以看到如下所示的输出-
    PUT URL:http://localhost:8080/products
    springboot excpt