您可以使用Spring Boot中的Interceptor在以下情况下执行操作 :
在发送请求之前到控制器
在向客户发送回复之前
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,你需要创建支持它的 @Component 类,它应该实现 HandlerInterceptor 接口.
以下是你使用的三种方法在拦截器和减号时应该知道;
preHandle()方法 : 这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 : 这用于在将响应发送给客户端之前执行操作.
afterCompletion()方法 : 这用于在完成请求和响应后执行操作.
观察以下代码以便更好地理解 :
@Componentpublic 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 {}}
你必须使用 WebMvcConfigurerAdapter 注册这个拦截器,如下所示 :
@Componentpublic class ProductServiceInterceptorAppConfig extends WebMvcConfigurerAdapter { @Autowired ProductServiceInterceptor productServiceInterceptor; @Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(productServiceInterceptor); }}
在下面给出的例子中,我们将点击GET产品API,它给出了下面给出的输出 :
Interceptor类ProductServiceInterceptor.java的代码在下面给出 :
package com .it1352.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;@Componentpublic 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"); }}
将Interceptor注册到拦截器注册表的Application Configuration类文件的代码 - ProductServiceInterceptorAppConfig.java在下面和下面给出;
package com.it1352.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;@Componentpublic class ProductServiceInterceptorAppConfig extends WebMvcConfigurerAdapter { @Autowired ProductServiceInterceptor productServiceInterceptor; @Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(productServiceInterceptor); }}
Controller类文件ProductServiceController.java的代码低于 :
package com.it1352.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.it1352.demo.exception.ProductNotfoundException;import com.it1352.demo.model.Product;@RestControllerpublic class ProductServiceController { private static MapproductRepo = 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
Product.java的POJO类代码低于 :
package com.it1352.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; }}
主要的Spring Boot应用程序类文件 DemoApplication.java 的代码如下 :
package com.it1352.demo; import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); }}
此处显示Maven build - pom.xml 的代码 :
4.0.0 com.IT屋 demo 0.0.1-SNAPSHOT jar demo Demo project for Spring Boot org.springframework.boot spring-boot-starter-parent 1.5.8.RELEASE UTF-8 UTF-8 1.8 org.springframework.boot spring-boot-starter-web org.springframework.boot spring-boot-starter-test test org.springframework.boot spring-boot-maven-plugin
此处显示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.IT屋'version = '0.0.1-SNAPSHOT'sourceCompatibility = 1.8repositories { mavenCentral()}dependencies { compile('org.springframework.boot:spring-boot-starter-web') testCompile('org.springframework.boot:spring-boot-starter-test')}
您可以创建一个可执行的JAR文件,并使用下面的Maven或Gradle com运行Spring Boot应用程序mands,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,请使用命令如下图所示 :
gradle clean build
"BUILD"之后"SUCCESSFUL",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
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,如下面给出的屏幕截图所示 :