模仿SpringMVC抽取一个BaseServlet，接收所有请求，然后自动封装表单参数和分发到对应的servlet执行，下面用一个页面表单提交，转发显示的项目做示例。
1）首先准备一个Entity，用来封装表单提交的参数
package com.qf.entity;
public class User {
private String name;
private String password;
private Integer age;
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "User [name=" + name + ", password=" + password + ", age=" + age + "]";
}
}User.java
2）前端表单
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="UserServlet?action=addUser" method="post">
姓名：<input type="text" name="name" /><br>
密码：<input type="text" name="password" /><br>
年龄：<input type="text" name="age" /><br>
<input type="submit" value="添加" /><br>
</form>
</body>
</html>
index.jsp
3）抽取BaseServlet，不需要再web.xml中注册，但要继承HttpServlet；主要通过反射来实现，具体的步骤已在代码中注释
package com.qf.servlet; import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Parameter; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; public class BaseServlet extends HttpServlet {
private static final long serialVersionUID = 1L; public BaseServlet() {
} protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String action = request.getParameter("action");
if (action != null && !"".equals(action)) {
Class<?> clazz = this.getClass(); // 获取当前执行的servlet的反射对象
Method[] methods = clazz.getDeclaredMethods(); // 获取反射对象的所有方法
for (Method method : methods) {
if (action.equals(method.getName())) { // 查询action是否有对应的方法
InvokeMethod(method, request, response); // 调用执行匹配的method
break;
}
}
}
} /**
* 执行method和封装param
* @param method
* @param request
* @param response
*/
private void InvokeMethod(Method method, HttpServletRequest request, HttpServletResponse response) {
try {
Object[] paramIns = packageParam(method, request, response); // 封装method的形参
String invoke = (String) method.invoke(this, paramIns); // 调用对应方法执行,就收返回结果
responseClient(invoke, request, response); // 响应客户端
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
} /**
* 封装method参数
* @param method
* @param request
* @param response
* @return
* @throws InstantiationException
*/
private Object[] packageParam(Method method, HttpServletRequest request, HttpServletResponse response) throws InstantiationException { Parameter[] parameters = method.getParameters(); // 获取method的所有参数
Object[] paramIns = new Object[parameters.length]; // 创建一个数组，用来保存处理后的参数 for (int i = 0; i < parameters.length; i++) { // 遍历参数
Class<?> paramObj = parameters[i].getType(); // 获取参数的Class
if ("HttpServletRequest".equals(paramObj.getSimpleName())) { // 处理 HttpServletRequest 参数
paramIns[i] = request;
} else if ("HttpServletResponse".equals(paramObj.getSimpleName())) { // 处理 HttpServletResponse 参数
paramIns[i] = response;
} else {
Object instance = null;
try {
instance = paramObj.newInstance(); // 实例化paramObj
} catch (IllegalAccessException e1) {
e1.printStackTrace();
}
Field[] fields = paramObj.getDeclaredFields(); // 获取paramObj所有的属性
try {
for (Field field : fields) { // 遍历属性
field.setAccessible(true); // 私有属性授权
String fieldName = field.getName(); // 获取属性名称
String value = request.getParameter(fieldName); // 根据属性名称从request中获取对应的值
Object val = null;
if (value != null && !"".equals(value)) {
val = changeParamType(value, field.getType()); // 把值类型转变为对应属性的类型
field.set(instance, val); // 把值赋给paramObj实例的对应属性
}
}
} catch (IllegalAccessException e) {
e.printStackTrace();
}
paramIns[i] = instance; // 保存参数
}
}
return paramIns;
} /**
* 表单数据类型转换
* @param value
* @param type
* @return
*/
private Object changeParamType(String value, Class<?> type) {
Object val = null; String name = type.getSimpleName(); // 获取类型名称
if ("String".equals(name)) {
val = value;
} else if ("Integer".equals(name)) {
val = Integer.parseInt(value);
} // 如有其他类型数据，else if 添加即可
return val;
} /**
* 解析执行结果
* @param invoke
* @param request
* @param response
*/
private void responseClient(String invoke, HttpServletRequest request, HttpServletResponse response) {
String[] split = invoke.split(":");
try {
if ("forward".equals(split[0])) {
request.getRequestDispatcher(split[1]).forward(request, response);
} else if ("redirect".equals(split[0])) {
response.sendRedirect(split[1]);
}
} catch (ServletException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
} protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
} }
BaseServlet.java
4）新建一个class，命名为UserServlet，UserServlet不需要继承HttpServlet，直接继承BaseServlet就可以了，但是要再在web.xml中注册；UserServlet中直接定义方法即可，但是方法名称必须和前端调用的名称保持一致
package com.qf.servlet;
import java.io.IOException;
import javax.servlet.http.HttpServletRequest;
import com.qf.entity.User;
@SuppressWarnings("all")
public class UserServlet extends BaseServlet {
public String addUser(User user, HttpServletRequest request) throws IOException {
request.setAttribute("user", user);
return "forward:test.jsp";
}
}UserServlet.java
5）编写一个test.jsp，接收响应
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h4>姓名：${user.name}</h4>
<h4>密码：${user.password}</h4>
<h4>年龄：${user.age}</h4>
</body>
</html>
test.jsp
6）验证
a) 启动tomcat，浏览器输入项目部署路径，进入index.jsp，填写数据，提交
b) test.jsp展示OK，抽取成功
7）第一次写博客，如有不正之处，还请指正，谢谢！