通用的servlet

痛定思痛。 2022-03-16 13:44 193阅读 0赞

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。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70][]

# 2 实例 #

## 2.1 目录结构 ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70 1][]

## 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 ##

![20190228080544243.gif][]

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。)

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70]: /images/20220316/b9177027ee894c3880cc1b868488a99c.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70 1]: /images/20220316/17b87c27c2134d94b04278a7fbaf9e59.png
[20190228080544243.gif]: /images/20220316/1215f99bdd9f4ca88a3a11551dec8029.png