Spring Boot Servlet过滤器

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，可以在两个实例上执行两个操作 -

在将请求发送到控制器之前
在向客户发送响应之前。
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，添加了System.out.println()语句来打印远程主机和远程地址。

package com.yiibai.demo;

import java.io.IOException; import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; import org.springframework.stereotype.Component; @Component public class SimpleFilter implements Filter { @Override public void destroy() {} @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 init(FilterConfig filterconfig) throws ServletException {} }

在Spring Boot主应用程序类文件中，添加了返回“Hello World”字符串的简单REST端点。

package com.yiibai.demo;

import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @SpringBootApplication @RestController public class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); } @RequestMapping(value = "/") public String hello() { return "Hello World"; } }

Maven构建配置文件：pom.xml 的代码如下 -

<?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.yiibai</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>

Gradle构建文件：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.yiibai'
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')
}

创建可执行的JAR文件，并使用下面显示的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

对于Maven，使用如下所示的命令 -

mvn clean install

在BUILD SUCCESS之后，在target目录下找到JAR文件。

对于Gradle，使用如下所示的命令 -

gradle clean build

在建立成功后，在build/libs 目录下找到JAR文件。

现在，使用以下命令运行JAR文件

java –jar <JARFILE>

在Tomcat端口8080上看到应用程序已启动。

现在点击URL => http://localhost:8080/ 并查看输出Hello World。它应该如下所示 -

然后，在控制台日志中看到远程主机和远程地址，如下所示 -

Spring Boot Servlet过滤器

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