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  Spring Boot Servlet 过滤器

  • Servlet 过滤器

    过滤器是一个对象，用于拦截应用程序的HTTP请求和响应。通过使用过滤器，我们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(拦截请求)
    • 在将响应发送给客户端之前(拦截响应)
    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 {}
}
    以下示例显示了用于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语句以打印远程主机和远程地址。 
    
package com.jc2182.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，我们添加了简单的REST端点，该端点返回“Hello World”字符串。 
    
package com.jc2182.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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.0.BUILD-SNAPSHOT</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.jc2182</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <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>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </repository>
        <repository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </pluginRepository>
        <pluginRepository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </pluginRepository>
    </pluginRepositories>

</project>
    下面给出了Gradle Build – build.gradle的代码- 
    
plugins {
    id 'org.springframework.boot' version '2.3.0.BUILD-SNAPSHOT'
    id 'io.spring.dependency-management' version '1.0.9.RELEASE'
    id 'java'
}

group = 'com.jc2182'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

repositories {
    mavenCentral()
    maven { url 'https://repo.spring.io/milestone' }
    maven { url 'https://repo.spring.io/snapshot' }
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    testImplementation('org.springframework.boot:spring-boot-starter-test') {
        exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
    }
}

test {
    useJUnitPlatform()
}
    您可以创建一个可执行的JAR文件，并使用Maven或Gradle命令运行Spring Boot应用程序-
    对于Maven，您可以使用以下命令- 
    
mvn clean install
    在“BUILD SUCCESS”之后，您可以在target目录下找到JAR文件。
    对于Gradle，您可以使用以下命令- 
    
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>
    在Tomcat端口8080上启动应用程序
    现在在浏览器访问 ： http://localhost:8080/
    springboot excpt
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