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