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Servlet 过滤器是用于拦截应用程序的 HTTP 请求和响应的对象。 通过使用过滤器,我们可以在两个实例上执行两个操作
以下代码显示了带有 @Component
注解的 Servlet 过滤器实现类的示例代码。
@Component
public class SimpleFilter implements Filter {
@Override
public void destroy() {}
@Override
public void doFilter
(ServletRequest request, ServletResponse response, FilterChain filterchain)
throws IOException, ServletException {}
@Override
public void init(FilterConfig filterconfig) throws ServletException {}
}
以下示例显示了在将请求发送到控制器之前从 ServletRequest 对象读取远程主机和远程地址的代码。
在 doFilter()
方法中,我们添加了 System.out.println
语句来打印远程主机和远程地址。
package com.study.filter;
import org.springframework.stereotype.Component;
import javax.servlet.Filter;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.FilterConfig;
import java.io.IOException;
@Component
public class SimpleFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {
System.out.println("Remote Host:"+request.getRemoteHost());
System.out.println("Remote Address:"+request.getRemoteAddr());
filterChain.doFilter(request, response);
}
@Override
public void destroy() {
}
}
在 Spring Boot 主应用程序类文件中,我们添加了返回 “Hello 迹忆客(jiyik.com)” 字符串的简单 REST 端点。
package com.study;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
/**
* @author jiyik.com
*/
@SpringBootApplication
public class MyApplication {
public static void main(String[] args) {
SpringApplication.run(MyApplication.class, args);
}
@RequestMapping(value = "/")
public String hello() {
return "Hello 迹忆客(jiyik.com)";
}
}
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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.spring</groupId>
<artifactId>springBootProject</artifactId>
<version>1.0-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.6.6</version>
</parent>
<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 的代码如下
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.study'
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')
}
这里我们使用 IDEA 来启动服务(读者也可以使用 mvn clean install
或者 gradle clean build
生成可执行jar包)
现在访问 URL http://localhost:8080/
并查看输出 Hello 迹忆客(jiyik.com)。 如下所示
然后,我们可以在控制台日志中看到远程主机和远程地址,如下所示