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 { 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 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 { 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.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> <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>
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-
祝学习愉快!(内容编辑有误?请选中要编辑内容 -> 右键 -> 修改 -> 提交!)
Tony Bai · Go语言第一课 -〔Tony Bai〕