servlet模拟SpringMVC

1. web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    version="3.1">
    <servlet>
        <servlet-name>DispatcherServlet</servlet-name>
        <servlet-class>amie.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>2</load-on-startup>
    </servlet>
    <servlet-mapping>
        <!-- servlet拦截下所有请求，交给DispatchServlet处理 -->
        <servlet-name>DispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

2. DispatcherServlet.java

public class DispatcherServlet extends HttpServlet {
 
    private static final long serialVersionUID = 116714888769576151L;
 
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
 
        try {
            // 获取请求URI
            String requestURI = request.getRequestURI();
            // 请求分发,根据不同请求URL，调用不同的业务处理器
            // 注意事项：一个处理器handler类，只有一个方法
            // 这个分发逻辑需要好好设计一下
            Object handler = null;
            // 首先根据请求URL，查找到对应的处理器
            if ("/queryUser".equals(requestURI)) {
                handler = new QueryUserHandler();
            } else if ("/addUser".equals(requestURI)) {
                handler = new AddUserHandler();
            }
            if (handler == null) {
                // 设置响应体的媒体类型
                response.setContentType("text/plain;charset=utf-8");
                // 响应
                response.getWriter().print("请求找不到");
                return;
            }
            // 其次再去调用对应处理器的方法
            if (handler instanceof QueryUserHandler) {
                ((QueryUserHandler) handler).handleRequest(request, response);
            }else if (handler instanceof AddUserHandler) {
                ((AddUserHandler) handler).handleRequest(request, response);
            }
 
            // 处理结果
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
 
}

3. HttpServletHandler.java（接口）

public interface HttpServletHandler {
    public void handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception;
}

4. AddUserHandler.java（处理器handler)

/***
 * 处理器：专门处理不同业务请求的
 */
public class AddUserHandler implements HttpServletHandler{
 
    public void handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
 
        // 设置响应体的媒体类型
        response.setContentType("text/plain;charset=utf-8");
        // 响应
        response.getWriter().print("添加成功");
    }
}