通用的servlet

1 通用的servlet实现的原理

2 实例

2.1 目录结构

2.2 BaseServlet.java

2.3 ServletDemo.java

2.4 index.html

2.5 test.html

2.6 运行结果

1 通用的servlet实现的原理

当页面向servlet发起请求时携带一个参数，我们的所有servlet继承自通用的BaseServlet,通用的servlet在取得参数后根据参数值执行子类servlet中的对应方法。

2 实例

2.1 目录结构

2.2 BaseServlet.java

package com.zhujunwei.servlet;

import java.io.IOException;
import java.lang.reflect.Method;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 接收要请求servlet所携带的方法名称，根据方法名称到相应的servlet去执行方法
 * @author zhujunwei
 * 2019年2月27日 下午11:18:13
 */
public class BaseServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;

	@Override
	public void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

		// localhost:8080/ServletDemo?method=addStu
		String method = req.getParameter("method");

		if (null == method || "".equals(method) || method.trim().equals("")) {
			method = "execute";
		}

		// 注意:此处的this代表的是子类的对象
		// 子类对象字节码对象
		Class<? extends BaseServlet> clazz = this.getClass();

		try {
			// 查找子类对象对应的字节码中的名称为method的方法.这个方法的参数类型是:HttpServletRequest.class,HttpServletResponse.class
			Method md = clazz.getMethod(method, HttpServletRequest.class, HttpServletResponse.class);
			if(null!=md){
				String jspPath = (String) md.invoke(this, req, resp);
				if (null != jspPath) {
					req.getRequestDispatcher(jspPath).forward(req, resp);
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}

	}

	// 默认方法
	public String execute(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		return null;
	}

}

2.3 ServletDemo.java

package com.zhujunwei.servlet ;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/ServletDemo")
public class ServletDemo extends BaseServlet {
	
	private static final long serialVersionUID = 1L;

	public ServletDemo(){}
	
	public String addStu(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		System.out.println("添加学生");
		return "test.html" ;
	}
	public String delStu(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		System.out.println("删除学生");
		return "test.html" ;
	}
	public String checkStu(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		System.out.println("检查学生");
		response.getWriter().println("zzz");
		return null ;
	}
}

2.4 index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script src="js/jquery-3.3.1.min.js" type="text/javascript"></script>
</head>
<body>
	
	<form action="ServletDemo?method=addStu" method="post">
		用户<input type="text" name="username" />
		<button>提交</button>
	</form>
	
	<a href="ServletDemo?method=delStu">删除学生</a><br>
	
	<button onclick="fu()">按钮</button>
</body>
<script>
	function fu() {
		$.post("ServletDemo", {
			"method" : "checkStu",
			"user" : "tom"
		}, function(data) {
			alert(data);
		});
	}
</script>
</html>

2.5 test.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
test
</body>
</html>

2.6 运行结果

可以看到，可以根据不同的方法名称执行不同的方法。

(有时候那个删除不执行，我也不知道为啥，以后解决。)

 

posted @ 2019-02-28 08:10  雨中遐想  阅读(4)  评论(0)  编辑  收藏  举报  来源