SpringBoot2 - Servlet

传统的Spring项目，配置Servlet需要在web.xml内添加对应的标签以及映射路径规则。

SpringBoot项目中如何创建Servlet以及自动装载到SpringBoot中？

构建项目

访问start.spring.io/
添加WEB依赖、Servlet依赖

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<dependency>
  <groupId>org.apache.tomcat.embed</groupId>
  <artifactId>tomcat-embed-jasper</artifactId>
</dependency>

<dependency>
  <groupId>javax.servlet</groupId>
  <artifactId>javax.servlet-api</artifactId>
</dependency>

创建Servlet

package com.gala.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 TestServlet extends HttpServlet {

    private static final long serialVersionUID = -2646554587718007415L;

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 设置返回类型为json
        resp.setContentType("application/json");
        // 设置返回字符集
        resp.setCharacterEncoding("UTF-8");
        // 输出对象
        PrintWriter writer = resp.getWriter();
        // 输出error消息
        writer.write("成功执行doGet方法");
        writer.close();
    }
}

使用Bean注册Servlet（单个Servlet）

新建ServletConfiguration配置类，并且添加一个@Bean的方法返回值为ServletRegistrationBean

package com.gala.servlet.conf;

import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import com.gala.servlet.TestServlet;

@Configuration
public class ServletConfiguration {

    @Bean
    public ServletRegistrationBean<TestServlet> servletRegistrationBean() {
        return new ServletRegistrationBean<TestServlet>(new TestServlet(), "/test");
    }
}

启动项目，访问地址：http://127.0.0.1:8080/test

SpringBoot自动装配Servlet（多个Servlet）

SpringBoot内部提供了注解@ServletComponentScan，这个注解的作用就是自动扫描我们SpringBoot项目内的有关Servlet配置，自动装配到我们的项目中。

TestServlet需要与ServletConfiguration同目录或在其子目录中

1. 修改ServletConfiguration，增加@ServletComponentScan

package com.gala.servlet.conf;

import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ServletComponentScan
public class ServletConfiguration {

}

2. 修改TestServlet，增加@WebServlet(urlPatterns = "/test2")

package com.gala.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 = "/test2")
public class TestServlet extends HttpServlet {

    private static final long serialVersionUID = -2646554587718007415L;

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 设置返回类型为json
        resp.setContentType("application/json");
        // 设置返回字符集
        resp.setCharacterEncoding("UTF-8");
        // 输出对象
        PrintWriter writer = resp.getWriter();
        // 输出error消息
        writer.write("成功执行doGet方法");
        writer.close();
    }
}

启动项目，访问地址：http://127.0.0.1:8080/test2