曾经觉得javabenan是一些java类.后来查看了一些百科
.javabean是java组件技术,又是遵循一些约定.不是非常理解.
什么是javabean?
?在jsp程序中用来封装业务逻辑,数据库操作与实体的类.
怎样理解上面的组件技术?
这些编写的java类,被放在一个特定的包中,能够打包这些类为jar等格式,复用性强,一次编译,可任意执行.
何为遵循特性约束?
1由 property,method,event组成.
2必须有public的无參构造函数
3类命名XXXBean
综合来看, javabean就是我们曾经封装的一个具无參构造函数的类,该类有属性方法等.
我们用实例来看
javabean中 User类
package com.bjpower.drp.sysmgr.domain;
import java.util.Date;
public class User {
public String getUserId() {
return userId;
}
public void setUserId(String userId) {
this.userId = userId;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getContactTel() {
return cOntactTel== null? "" : contactTel;
}
public void setContactTel(String contactTel) {
this.cOntactTel= contactTel;
}
public String getEmail() {
return email == null ?
"" : email;
}
public void setEmail(String email) {
this.email = email;
}
public Date getCreateDate() {
return createDate;
}
public void setCreateDate(Date createDate) {
this.createDate = createDate;
}
// userID
private String userId;
// username
private String userName;
// password
private String password;
private String contactTel;
private String email;
// util Date
private Date createDate;
}
该类中,我们将成员变量设置为private,将属性设置为public,而且为getXXXX(变量名).
Control类
package com.bjpower.sysmgr;//c+f+o
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import com.bjpower.drp.sysmgr.domain.User;
import com.bjpower.drp.util.DbUtil;
import com.bjpower.drp.util.PageModel;
/**
* 採用单例模式
* @author v-hanyk
*
*/
public class userManager {
private static userManager instance=null;
private userManager(){
}
//入口方法
public static synchronized userManager getUserMangwer(){
if(instance== null){
instance = new userManager();
}
return instance;
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// 必须显示调用父类方法
if (Constants.ADD.equals(GetCommand())) {
add(req, resp);
} else if (Constants.DEL.equals(GetCommand())) {
delete(req, resp);
} else if (Constants.MOIDFY.equals(GetCommand())) {
modify(req, resp);
} else if (Constants.SHOW_ADD.equals(GetCommand())) {
showAdd(req, resp);
} else if (Constants.QUERY.equals(GetCommand())) {
//查询
findUserById(req, resp);
}
}
/**
* 依据用户代码查询用户
* @param req
*@param resq
* @return
* @throws SQLException
*/
public void findUserById(HttpServletRequest req, HttpServletResponse resp) throws Exception {
StringBuffer sql= new StringBuffer();
sql.append("select user_id, user_name, password, contact_tel, email, create_date from t_user where user_id= ?");
Connection cOnn=null;
PreparedStatement pstmt=null;
ResultSet rs= null;
User user=null;
String userId=req.getParameter("userId");
try{
cOnn= DbUtil.getconnection();
pstmt=conn.prepareStatement(sql.toString());
pstmt.setString(1, userId);
rs=pstmt.executeQuery();
if(rs.next()){
user=new User();
user.setUserId(rs.getString("user_id"));
user.setUserName(rs.getString("user_name"));
user.setPassword(rs.getString("password"));
user.setContactTel(rs.getString("contact_tel"));
user.setEmail(rs.getString("email"));
user.setCreateDate(rs.getTimestamp("create_date"));
}
req.setAttribute("user", user);
//转发。带resq与resq,若是重定向。则没有req，resq则没有数据
resp.getRequestDispatcher("flowcard/modifyuser.jsp").forward(req, resp);
}catch(SQLException e){
e.printStackTrace();
}finally{
DbUtil.close(rs);
DbUtil.close(pstmt);
DbUtil.close(conn);
}
return user;
}
}
?
Control类是一个简单的业务处理类。
View页面获取javaBean中数据
通过EL表达式
用户代码:? | size="10" maxlength="10" readOnly="true" value=${user.Id}> |
*用户名称:? | size="20" maxlength="20" value=${user.userName}> |
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