Spring Boot 环境下的 Servlet 配置与使用

准备

新建 Spring Boot Starter Project

使用 IntelliJ IDEA 创建一个新的 Maven 项目

添加 Spring Boot Starter Web 依赖到 pom.xml 中


   
    
    
        
     
      org.springframework.boot
     
        
     
      spring-boot-starter-web

新建一个 Servlet 类，位于 src/main/java/com/mk/servlet/HelloServlet.java，内容如下：

package com.mk.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class HelloServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    public HelloServlet() {
        System.out.println("HelloServlet.HelloServlet()");
    }
    @Override
    public void init() throws ServletException {
        System.out.println("HelloServlet.init()");
    }
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("HelloServlet.doGet()");
        PrintWriter writer = response.getWriter();
        writer.write("Hello, " + request.getRemoteAddr());
        writer.flush();
        writer.close();
    }
    @Override
    public void destroy() {
        System.out.println("HelloServlet.destroy()");
    }
}

配置类

创建一个配置类 ServletComponentConfiguration.java，位于 src/main/java/com/mk/configuration/ServletComponentConfiguration.java，内容如下：

package com.mk.configuration;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ServletComponentScan(basePackages = {"com.mk.servlet"})
public class ServletComponentConfiguration {
}

启动类

创建一个启动类 SpringBootServletApplication.java，位于 src/main/java/com/mk/SpringBootServletApplication.java，内容如下：

package com.mk;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class SpringBootServletApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootServletApplication.class, args);
    }
}

通过 Spring Bean 注册 Servlet

编辑 ServletComponentConfiguration.java，添加以下代码：

package com.mk.configuration;
import java.util.Arrays;
import javax.servlet.Servlet;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.mk.servlet.HelloServlet;
@Configuration
public class ServletComponentConfiguration {
    
    @Bean
    public ServletRegistrationBean servletRegistration() {
        ServletRegistrationBean registration = new ServletRegistrationBean();
        registration.setServlet(new HelloServlet());
        registration.setUrlMappings(Arrays.asList("/hello"));
        return registration;
    }
}

启动应用后，控制台会输出：

HelloServlet.HelloServlet()
HelloServlet.init()

表示 Servlet 已经成功注册到 Spring Boot 容器中。

使用类路劲扫描注册 Servlet

编辑 HelloServlet.java，添加 @WebServlet 注解：

package com.mk.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(urlPatterns = "/hello")
public class HelloServlet extends HttpServlet {
    // ... 保持不变
}

编辑 ServletComponentConfiguration.java，删除相关代码，并添加 @ServletComponentScan 注解：

package com.mk.configuration;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ServletComponentScan(basePackages = {"com.mk.servlet"})
public class ServletComponentConfiguration {
}

启动应用后，访问 /hello URL 应该能够正常工作。