Spring Boot Servlet過濾器

過濾器是用於攔截應用程序的HTTP請求和響應的對象。通過使用過濾器，可以在兩個實例上執行兩個操作 -

在將請求發送到控制器之前
在向客戶發送響應之前。
以下代碼顯示了帶有[@Component](https://github.com/Component "@Component")註解的Servlet過濾器實現類的示例代碼。

@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 {}
}

以下示例顯示了在將請求發送到控制器之前從ServletRequest對象讀取遠程主機和遠程地址的代碼。

在doFilter()方法中，添加了System.out.println()語句來打印遠程主機和遠程地址。

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主應用程序類文件中，添加了返回「Hello World」字符串的簡單REST端點。

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構建配置文件：pom.xml 的代碼如下 -

<?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構建文件：build.gradle 的代碼如下 -

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')
}

創建可執行的JAR文件，並使用下面顯示的Maven或Gradle命令運行Spring Boot應用程序 -

對於Maven，使用如下所示的命令 -

mvn clean install

對於Maven，使用如下所示的命令 -

mvn clean install

在BUILD SUCCESS之後，在target目錄下找到JAR文件。

對於Gradle，使用如下所示的命令 -

gradle clean build

在建立成功後，在build/libs 目錄下找到JAR文件。

現在，使用以下命令運行JAR文件

java –jar <JARFILE>

在Tomcat端口8080上看到應用程序已啓動。

現在點擊URL => http://localhost:8080/ 並查看輸出Hello World。它應該如下所示 -
Spring

然後，在控制檯日誌中看到遠程主機和遠程地址，如下所示 -

Spring

Spring Boot教程