myEclipse,web项目连接数据库

下面的结构图

1.在src你创建com.hqyj.wj.model建立model包,model里放数据库的元素,User.java的截图

package com.hqyj.wj.model;
//用户信息表
public class User {
	 private int id;
	 private String name;
	 private String birthday;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getBirthday() {
		return birthday;
	}
	public void setBirthday(String birthday) {
		this.birthday = birthday;
	}
}

　　

2.在src你创建com.hqyj.wj.dao.inf建立包,这个包是放接口类,这是UserDaoInf的截图

package com.hqyj.wj.dao.inf;
import java.util.List;
import com.hqyj.wj.model.User;
/**
 * 数据访问层的接口定义数据接口的方法
 * 
 */
public interface UserDaoInf {
 //定义一个查询方法
	List<User> search();
	
}

3.在src你创建com.hqyj.wj.dao建立包,这个包连接数据库,及实现上面的接口类

package com.hqyj.wj.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import com.hqyj.wj.dao.inf.UserDaoInf;
import com.hqyj.wj.model.User;

/**
 * 
 * @author wl 数据访问接口
 */
public class UserDao implements UserDaoInf {
	// 数据访问数据库的连接对象
	protected Connection con = null;
	//预编译你写的sql语句
	protected PreparedStatement ps=null;
	//查询预编译的sql语句
	protected ResultSet  rs=null;
	
	
	// 获取数据库链接
	@SuppressWarnings("finally")
	public Connection getCon() {
		try {
			// 加载mysql驱动
			Class.forName("com.mysql.jdbc.Driver");
			//获取数据库链接
			con=DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/image?characterEncoding=utf8", "root", "root");
			System.out.println("链接成功");
			return con;
		} catch (Exception e) {
			System.out.println("链接失败"+e.getMessage());
			return null;
		
//		} finally {
//			try {
//				con.close();
//			} catch (SQLException e) {
//				// TODO Auto-generated catch block
//				e.printStackTrace(); 
//				return null;
//			}
			//
		}

	}
/**
 * 查询方法
 */
	
	public List<User> search() {
		List<User> list=new ArrayList<User>();
		try {
			//定义一个sql语句
			//String sql="SELECT a.id as 序号,a.salary as '薪水',b.`name` as '姓名'  from salary a LEFT JOIN `user` b on a.u_id=b.id";
			 String sql="SELECT * from user";
			 //获取数据库连接
			 con=getCon(); 
			 //预编译sql语句
			ps=con.prepareStatement(sql);
			 //把编译出来的结果集装载到ResultSet对象里面
			 rs=ps.executeQuery();
			// rs=statement.executeQuery(sql);
			 //取出ResultSet里的结果集装载到数据模型里
			 while(rs.next()){
				 User user=new User();
				 user.setName(rs.getString("name"));
				 user.setBirthday(rs.getString("birthday"));
				 user.setId(Integer.parseInt(rs.getString("id")));
                  list.add(user);
			 }
		} catch (Exception e) {
			System.out.println("查询错误"+e.getMessage());
		}finally{
			try {
				rs.close();
				ps.close();
				con.close();
			} catch (Exception e2) {
				e2.printStackTrace();
			}
		}

		return list;
	}

}

　

5.要引入数据库包mysql-connector-java-commercial-5.1.25-bin.jar,和json-lib-2.2.3-jdk15.jar在项目名字上右键->properties->java Build Path->Libraries->Add External Jars然后选择你下载的包

6.在src下面创建测试类

　　

import java.util.List;

import com.hqyj.wj.dao.UserDao;
import com.hqyj.wj.model.User;
public class Test {

/**
* @param args
*/
public static void main(String[] args) {
//获取数据库访问类对象
UserDao dao=new UserDao();
dao.getCon();
List<User> list=dao.search();
for(int i=0;i<list.size();i++){
System.out.println("id=="+list.get(i).getId());
System.out.println("name=="+list.get(i).getName());
System.out.println("birthday=="+list.get(i).getBirthday());
}
}

}

　　

7.成功显示

8.src创建服务类和接口,UserServiceInf和UserService

package com.hqyj.wj.service.inf;

import java.util.List;

import com.hqyj.wj.model.User;

public interface UserServiceInf {
	List<User> search();
}

package com.hqyj.wj.service;

import java.util.List;

import com.hqyj.wj.dao.UserDao;
import com.hqyj.wj.dao.inf.UserDaoInf;
import com.hqyj.wj.model.User;
import com.hqyj.wj.service.inf.UserServiceInf;

/**
 *逻辑服务层实现类
 */
public class UserService implements UserServiceInf{
	UserDaoInf us=new UserDao();
	public List<User> search() {
		
		return us.search();
	}
 
}

9.src创建控制层　,下新建个服务

package com.hqyj.wj.controller;

import java.io.IOException;
import java.io.PrintWriter;

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

import net.sf.json.JSONArray;

import com.hqyj.wj.service.*;
import com.hqyj.wj.service.inf.*;
import com.hqyj.wj.model.*;

import java.util.List;
import java.util.ArrayList;

public class OneServlet extends HttpServlet {

	public OneServlet() {
		super();
	}

	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}
  //doget对应的是ajax的$.get()方法
  //request是装载请求数据
//response响应数据到前端对象
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
      		//解决中文乱码的问题
		request.setCharacterEncoding("utf-8");
		response.setCharacterEncoding("utf-8");
		//在服务器端设置允许在其他域名下访问，及响应类型、响应头设置
		System.out.println("这是");
		response.setHeader("Access-Control-Allow-Origin", "*");
		response.setHeader("Access-Control-Allow-Methods","POST");
		response.setHeader("Access-Control-Allow-Headers","x-requested-with,content-type");
		  //响应的文本格式
		response.setContentType("text/html");
		//获取响应的输出对象
		PrintWriter out = response.getWriter();
//		out.print("nissssss");
//		out.print("您好呀");
		
		//创建服务器层实现类
		UserServiceInf service=new UserService();
		List<User> list=service.search();
		//把list数据解析成前端页面能读取的数据
		JSONArray json=JSONArray.fromObject(list);
		out.print(json.toString());
		out.flush();
		out.close();
	}
	  //doget对应的是ajax的$.post()方法
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("text/html");
		PrintWriter out = response.getWriter();
		out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">");
		out.println("<HTML>");
		out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
		out.println("  <BODY>");
		out.print("    This is ");
		out.print(this.getClass());
		out.println(", using the POST method");
		out.println("  </BODY>");
		out.println("</HTML>");
		out.flush();
		out.close();
	}

	public void init() throws ServletException {
		// Put your code here
	}

}

10.新建一个html,获取数据库数据

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>ajax获取集合</title>
    <script src="../js/jquery-3.1.1.min.js"></script>
</head>
<body>
<table>
    <thead>
   <tr><th>id</th>
   <th>姓名</th>
   <th>生日</th></tr>
    </thead>
    <tbody>
    </tbody>
</table>
<script>
    $(function(){
        $.get("http://localhost:8080/jquery/servlet/OneServlet",function(data){
           var num=eval(data);
            var str;

//            for(var o in num){
//                console.log(num[o].name);
//                str+=" <tr> <td>"+num[o].id+"</td> <td>"+num[o].name+"</td> <td>"+num[o].birthday+"</td></tr>";
//                $("tbody").html(str)
//            }
for(var i=0;i<num.length;i++){
    str+=" <tr> <td>"+num[i].id+"</td> <td>"+num[i].name+"</td> <td>"+num[i].birthday+"</td></tr>";
}
            $("tbody").html(str)
        })
    })
</script>
</body>
</html>

11.就可以运行成功了,我最开始运行失败了,把tomcat7换为tomcat6就正确了