JDBC（Java Database Connectivity）是Java SE平台的一种标准API，它提供了一种标准的方法来访问关系型数据库，使得Java程序能够与各种不同的数据库进行交互，这篇文章我们来进行实验体验一下。

自定义JDBC连接工具类
1.编写第一代JDBCUtils并测试查看结果
第一代JDBCUtils：

package com.javaweb.utils;
import java.io.FileReader;
import java.sql.*;
import java.util.Properties;

public class JDBCUtils2 {
  private static String driver;
  private static String url;
  private static String user;
  private static String password;
static {
  try {
    // 1. 创建Properties集合类。
      Properties properties = new Properties();
    // 2. 加载文件
    properties.load(new FileReader(JDBCUtils.class.getClassLoader().getResource("jdbc.properties").getPath()));
 driver = properties.getProperty("driver");
 url = properties.getProperty("url");
 user = properties.getProperty("user");
 password = properties.getProperty("password");
 // 注册驱动
 Class.forName(driver);
 } catch (Exception e) {
   e.printStackTrace();
 }
 }
public static Connection getConnection() throws SQLException { 
	   return   DriverManager.getConnection(url, user, password);
	}

	// 释放资源
	public static void close(ResultSet rs, PreparedStatement pstm, Connection conn) {
	try {
	     if (rs != null) {
	       rs.close();
	     }
	     if (pstm != null) {
	        pstm.close();
	     }
	     if (conn != null) {
	        conn.close();
	     }
	     } catch (SQLException e) {
	         e.printStackTrace();
	    }
	}
}

第一代JDBCUtils测试:

package com.javaweb.utils;

import java.sql.*;

public class testJdbcUtils1 {
	public static void main(String[] args) throws Exception {
		Connection conn = JDBCUtils.getconnection();
		String sql="update account set money = ? where id = ?";
		PreparedStatement pstm = conn.prepareStatement(sql);
		pstm.setString(1, "20000");
		pstm.setString(2, "1");
		int count=pstm.executeUpdate();
		JDBCUtils.close( null,pstm, conn);
		System.out.println(count);
	}
}

2.编写第二代JDBCUtils并测试查看结果
在src下创建数据库连接配置文件：jdbc.properties

第二代JDBCUtils代码：

package com.javaweb.utils;
import java.io.FileReader;
import java.sql.*;
import java.util.Properties;

public class JDBCUtils2 {
  private static String driver;
  private static String url;
  private static String user;
  private static String password;
static {
  try {
    // 1. 创建Properties集合类。
      Properties properties = new Properties();
    // 2. 加载文件
    properties.load(new FileReader(JDBCUtils.class.getClassLoader().getResource("jdbc.properties").getPath()));
 driver = properties.getProperty("driver");
 url = properties.getProperty("url");
 user = properties.getProperty("user");
 password = properties.getProperty("password");
 // 注册驱动
 Class.forName(driver);
 } catch (Exception e) {
   e.printStackTrace();
 }
 }
public static Connection getConnection() throws SQLException { 
	   return   DriverManager.getConnection(url, user, password);
	}

	// 释放资源
	public static void close(ResultSet rs, PreparedStatement pstm, Connection conn) {
	try {
	     if (rs != null) {
	       rs.close();
	     }
	     if (pstm != null) {
	        pstm.close();
	     }
	     if (conn != null) {
	        conn.close();
	     }
	     } catch (SQLException e) {
	         e.printStackTrace();
	    }
	}
}

第二代JDBCUtils测试：

package com.javaweb.utils;
import java.sql.*;
public class testJdbcUtils2 {
	public static void main(String[] args) throws Exception {
		Connection conn = JDBCUtils2.getConnection();
		String sql = "update account set money = ? where id = ?";
		PreparedStatement pstmt = conn.prepareStatement(sql);
		pstmt.setDouble(1, 50000);
		pstmt.setInt(2, 1);
		int count = pstmt.executeUpdate();
		System.out.println(count);
	}
}

封装增删改查DAO
1.搭建数据库环境，创建库tb_user,插入测试记录
在MySQL中创建一个名称为db的数据库，然后在该数据库中创建一个tb_user表，再向表中插入3条数据。

create database db charset=utf8;
CREATE TABLE tb_user(
     id INT PRIMARY KEY AUTO_INCREMENT,
     username VARCHAR(40),
     password VARCHAR(40),
     email VARCHAR(60),
     birthday DATE 
)CHARACTER SET utf8 COLLATE utf8_general_ci;
INSERT INTO tb_user(username,password ,email,birthday) VALUES('zs','123456','zs@sina.com','1980-12-04');
INSERT INTO tb_user(username,password ,email,birthday) VALUES('lisi','123456','lisi@sina.com','1981-12-04');
INSERT INTO tb_user(username,password ,email,birthday) VALUES('wangwu','123456','wangwu@sina.com','1979-12-04');

2.创建JavaBean：User.java
在src目录下，新建一个名称为chapter02.jdbc.example的包
创建JavaBean，User类的具体实现方式如下：

package com.javaweb.bean;


import java.util.Date;
 
	public class user {
		private int id;
		public int getId() {
			return id;
		}
		public void setId(int id) {
			this.id = id;
		}
		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 getEmail() {
			return email;
		}
		public void setEmail(String email) {
			this.email = email;
		}
		public Date getBirthday() {
			return birthday;
		}
		public void setBirthday(Date birthday) {
			this.birthday = birthday;
		}
		private String username;
		private String password;
		private String email;
		private Date birthday;
	}

创建数据库访问层DAO类封装增删改查代码：UserDao.java

package chapter02.jdbc.example;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.text.SimpleDateFormat;
import java.util.ArrayList;

import com.javaweb.bean.user;

 
public class UsersDao {
	//添加用户的操作
	public boolean insert(user user) {
		Connection conn = null;
		Statement stmt=null;
		ResultSet rs = null;
		try {
			conn = JDBCUtils.getConnection();
			stmt = conn.createStatement();
			SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
			String birthday = sdf.format(user.getBirthday());
			String sql = "INSERT INTO tb_user(id,username,password,email,birthday)"+
						"VALUES("
						+user.getId()
						+",'"
						+user.getUsername()
						+"','"
						+user.getPassword()
						+"','"
						+user.getEmail()
						+"','"
						+birthday + "')";
			System.out.println(sql);
			int num = stmt.executeUpdate(sql);
			if (num > 0) {
				return true;
			}
			return false;
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCUtils.release(rs,stmt,conn);
		}
		return false;
	}
	
	public ArrayList<user> findAll(){
		Connection conn = null;
		Statement stmt=null;
		ResultSet rs = null;
		ArrayList<user> list = new ArrayList<user>();
		try {
			conn = JDBCUtils.getConnection();
			stmt = conn.createStatement();
			String sql = "SELECT * FROM tb_user";
			rs = stmt.executeQuery(sql);
			while(rs.next()) {
				user user = new user();
				user.setId(rs.getInt("id"));
				user.setUsername(rs.getString("username"));
				user.setPassword(rs.getString("password"));
				user.setEmail(rs.getString("email"));
				user.setBirthday(rs.getDate("birthday"));
				list.add(user);
			}
			return list;
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCUtils.release(rs, stmt, conn);
		}
		return null;
	}
	public user find(int id) {
		Connection conn=null;
		Statement stmt=null;
		ResultSet rs = null;
		try {
			conn = JDBCUtils.getConnection();
			stmt=conn.createStatement();
			String sql = "SELECT * FROM tb_user WHERE id=" + id;
			rs = stmt.executeQuery(sql);
			while(rs.next()) {
				user user = new user();
				user.setId(rs.getInt("id"));
				user.setUsername(rs.getString("username"));
				user.setPassword(rs.getString("password"));
				user.setEmail(rs.getString("email"));
				user.setBirthday(rs.getDate("birthday"));
				return user;
			}
			return null;
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCUtils.release(rs,stmt, conn);
		}
		return null;
	}
	public boolean delete(int id) {
		Connection conn = null;
		Statement stmt = null;
		ResultSet rs = null;
		try {
			conn = JDBCUtils.getConnection();
			stmt= conn.createStatement();
			String sql = "DELETE FROM tb_user WHERE id=" + id;
			int num =stmt.executeUpdate(sql);
			if(num > 0) {
				return true;
			}
			return false;
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCUtils.release(rs, stmt,conn);
		}
		return false;
	}
	public boolean update(user user) {
		Connection conn =null;
		Statement stmt = null;
		ResultSet rs = null;
		try {
			conn= JDBCUtils.getConnection();
			stmt = conn.createStatement();
			SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
			String birthday =sdf.format(user.getBirthday());
			String sql = "UPDATE tb_user set username='"+user.getUsername()
						+"',password='"+user.getPassword() + "',email='"
						+user.getEmail() + "',birthday='" + birthday
						+"'WHERE id=" + user.getId();
			int num = stmt.executeUpdate(sql);
			if (num > 0) {
				return true;
			}
			return false;
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			JDBCUtils.release(rs, stmt, conn);
		}
		return false;
	}
}

4.利用JUnit对DAO的方法进行单元测试，并查看结果
创建测试类JDBCTESTl，利用JUnit对DAO-insert方法添加tb_user表中的数据:

在这里插入代码片`package chapter02.jdbc.example;


import java.util.Date;

import com.javaweb.bean.user;

@Test
public class JDBCTest {
	public static void main(String[] args) {
		//向users表插入一个用户信息
		UsersDao ud = new UsersDao();
		user user=new user();
		user.setId(4);
		user.setUsername("xiaoli");
		user.setPassword("00000");
		user.setEmail("h23526456@qq.com");
		user.setBirthday(new Date());
		boolean b= ud.insert(user);
		System.out.println(b);
	}
	
}`

测试结果：

创建测试类JDBCTEST03，利用JUnit对DAO-findAll方法根据ID查询tb_user表中数据：

package chapter02.jdbc.example;


import java.util.ArrayList;

import com.javaweb.bean.user;
 
public class FindAllUsersTest {
	public static void main(String[] args) {
		UsersDao usersDao = new UsersDao();
		ArrayList<user> list = usersDao.findAll();
		for (int i=0; i< list.size(); i++) {
			System.out.println("第" + (i+1) + "条数据的username的值为："
					+list.get(i).getUsername());
		}
	}
 
}

测试结果，成功查询出tb_user表中所有username值：

创建测试类JDBCTEST03，利用JUnit对DAO-find方法根据ID查询tb_user表中数据：
我们根据ID查询tb_user表中ID为13的数据库信息：

package chapter02.jdbc.example;

import static org.junit.Assert.*;

import org.junit.Test;

import com.javaweb.bean.user;

public class JDBCTEST03 {

	
	@Test
	public void testFind() throws Exception {
	UsersDao dao= new UsersDao();
	user user=dao.find(13);
	System.out.println("id为13的User对象的name值为："+user.getUsername());
	}


}

测试结果：
成功通过ID查询rb_user表中ID为13的username信息

创建测试类JDBCTEST04，利用JUnit对DAO-update方法方法根据ID更新tb_user表中数据：

package chapter02.jdbc.example;

import java.util.Date;

import org.junit.Test;

import com.javaweb.bean.user;

public class JDBCTEST04 {

	@Test
	public void testUpdate() throws Exception {
	        UsersDao dao= new UsersDao();
	        user user=new user();
	        user.setId(13);
	        user.setUsername("项秀才让");
	        user.setPassword("abc");
	        user.setEmail("123456@sina.com");
	        user.setBirthday(new Date());
	        boolean b=dao.update(user);
	        System.out.println(b);
	}

}

测试结果：
成功修改ID为13的数据库记录信息！

创建测试类JdbcTest01，利用DAO-delete方法删除tb_user表中的数据

package chapter02.jdbc.example;
import org.junit.jupiter.api.Test;
class JdbcTest01 {

	@Test
	public void testDelete() {
	   UsersDao dao= new UsersDao();
	   boolean b=dao.delete(8);
	   System.out.println(b);
	}	
}

测试结果和sql查询结果：

用户登录程序
1.创建数据库表
在MySQL中使用一个名称为db_myweb的数据库，然后在该数据库中创建一个tb_user表，再向表中插入3条数据。

在这里插入代码片`Use db_myweb；
CREATE TABLE tb_user(
     id INT PRIMARY KEY AUTO_INCREMENT,
     username VARCHAR(40),
     password VARCHAR(40),
     email VARCHAR(60),
     birthday DATE 
)CHARACTER SET utf8 COLLATE utf8_general_ci;
插入数据：
INSERT INTO tb_user(username,password ,email,birthday) VALUES('zs','123456','zs@sina.com','1980-12-04');
INSERT INTO tb_user(username,password ,email,birthday) VALUES('lisi','123456','lisi@sina.com','1981-12-04');
INSERT INTO tb_user(username,password ,email,birthday) VALUES('wangwu','123456','wangwu@sina.com','1979-12-04');
`

2.编写登录页面
在web目录下创建一个名称为login的JSP文件，在该文件中添加用于用户登录时输入用户信息的表单元素。

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="/myweb/LoginServlet" method="post">
用户名：<input type="text" name="username">     <br>
密  码：<input type="password" name="password"> <br> 
<input type="submit" value="登录">
</form>
</body>
</html>

3.编写工具类
由于每次操作数据库时，都需要加载数据库驱动、建立数据库连接以及关闭数据库连接，为了避免代码的重复书写，所以需要建立一个专门用于操作数据库的工具类。在src下创建一个包com.javaweb.utils，在包中创建一个封装了上述操作的工具类JDBCUtils。

package com.javaweb.utils;

import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.mysql.jdbc.Connection;

public class JDBCUtils {
	  // 加载驱动
	  static {
	  try {
	    Class.forName("com.mysql.jdbc.Driver");
	  } catch (ClassNotFoundException e) {
	    e.printStackTrace();
	  }
	  }
	// 获取连接
	public static Connection getconnection() throws Exception {
	   String url = "jdbc:mysql://localhost:3306/db_myweb?useSSL=false";
	   String user = "root";
	   String password = "root";
	   Connection conn = (Connection) DriverManager.getConnection(url, user, password);
	   return conn;
	}
	// 释放资源
	public static void close(ResultSet rs, java.sql.PreparedStatement pstm, java.sql.Connection conn) {
	try {
	     if (rs != null) {
	       rs.close();
	     }
	     if (pstm != null) {
	        pstm.close();
	     }
	     if (conn != null) {
	        conn.close();
	     }
	     } catch (SQLException e) {
	         e.printStackTrace();
	    }
	 }
	}

4.UserDao增加方法按用户名和密码查询方法

// 根据username,password查找指定的user
public boolean findByUsernameAndPassword(String username,String password){
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
try {
// 获得数据的连接
conn = JDBCUtils.getConnection();
// 发送SQL语句
String sql = "select * from tb_user where username=? and password=?";
// 获得PreparedStatement对象
pstmt = (PreparedStatement) conn.prepareStatement(sql);
pstmt.setString(1, username);
pstmt.setString(2, password);
rs = pstmt.executeQuery();
// 处理结果集
if (rs.next()) 
return true;
return false;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(rs, pstmt, conn);
}
return false;
}

5.实现登录功能的LoginServlet

package com.javaweb.servlet;

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

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

/**
 * Servlet implementation class LoginServlet
 */
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     request.setCharacterEncoding("UTF-8");
     response.setContentType("text/html;charset=utf-8"); 
     PrintWriter out = response.getWriter();
     String username=request.getParameter("username");
     String password=request.getParameter("password");
     if(username!=null&&password!=null&&!username.equals("")&&!password.equals("")) {
          UserDao dao=new UserDao();
          boolean b=dao.findByUsernameAndPassword(username, password);
          if(b)
	  out.print("欢迎登录！");
          else
	  out.print("用户名或密码不正确！");	
          }else
	   out.print("用户名或密码不能为空！");	
    }

}

运行项目，查看效果





C3P0数据库连接池实验
1.导入JAR包c3p0-0.9.2.1.jar和mchange-commons-java-0.2.3.4.jar
在项目中导入JAR包c3p0-0.9.2.1.jar和mchange-commons-java-0.2.3.4.jar，并使用C3P0数据库连接池对象获取Connection对象。

2.创建C3P0Test测试用例类，测试代码

package com.javaweb.test;


import java.sql.Connection;
import java.sql.SQLException;

import org.junit.Test;


import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3P0Test {

@Test
public void test() throws PropertyVetoException, SQLException, java.beans.PropertyVetoException {
ComboPooledDataSource ds = new ComboPooledDataSource();
ds.setDriverClass("com.mysql.jdbc.Driver");
ds.setJdbcUrl("jdbc:mysql://localhost:3306/db_myweb?useSSL=false");
ds.setUser("root");
ds.setPassword("root");
ds.setInitialPoolSize(5);
ds.setMaxPoolSize(10);
Connection conn = ds.getConnection();
System.out.println(conn);
}


}

测试结果：

3.在项目的src根目录下创建一个c3p0-config.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
<default-config>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl"> jdbc:mysql://localhost:3306/db_myweb?useSSL=false</property>
<property name="user">root</property>
<property name="password">root</property>
<property name="checkoutTimeout">30000</property>
<property name="initialPoolSize">10</property>
<property name="maxIdleTime">30</property>
<property name="maxPoolSize">10</property>
<property name="minPoolSize">2</property>
<property name="maxStatements">200</property>
</default-config>
</c3p0-config>

4.创建C3P0Test测试用例类，测试代码

package chapter02.jdbc.example;

import java.beans.PropertyVetoException;
import java.sql.SQLException;

import org.junit.Test;

import com.mchange.v2.c3p0.ComboPooledDataSource;
import com.mysql.jdbc.Connection;

public class C3P0Test {


@Test
public void testC3P0() throws SQLException {
ComboPooledDataSource ds= new ComboPooledDataSource();
System.out.println(ds.getConnection());
}
}

测试结果：
测试成功！

5.封装DataSourceUtils工具类

package com.javaweb.test;

import java.sql.SQLException;

import com.mysql.jdbc.Connection;

public class DataSourceUtils {
    private static ComboPooledDataSource ds=new ComboPooledDataSource();
    public static ComboPooledDataSource getDataSource()
    {
        return  ds;
    }
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }
}

6.修改UserDao从DataSourceUtils工具类，获取数据库连接，并测试结果。

BUtils工具增删改查
1.将commons-dbutils-1.7.jar添加到项目的lib目录中

2.创建UserDaoQr.java，编写QueryRunner示例代码：增加、删除、修改

package cn.itcast.jdbc.dao;

import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;

import cn.itcast.jdbc.javabean.User;
import cn.itcast.jdbc.utils.DataSourceUtils;

public class UserDaoQr {
public boolean insert(User user) throws SQLException {
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "INSERT INTO t_user(id,username,password) VALUES(null,?,?)";
int num= r.update(sql,user.getName(),user.getPassword());
if (num > 0) {
return true;
}
return false;
}
public boolean update(User user) throws SQLException {
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "update t_user set username=?,password=?";
int num= r.update(sql,user.getName(),user.getPassword());
if (num > 0) {
return true;
}
return false;
}

public boolean delete(int id) throws SQLException {
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "delete from t_user where id=?";
int num= r.update(sql,id);
if (num > 0) {
return true;
}
return false;
}

public User find(int id) throws SQLException{
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "SELECT * FROM user WHERE id=?";
User user= r.query(sql, new BeanHandler<User>(User.class),id);
return user;
}
public List<User> findAll() throws SQLException{
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "SELECT * FROM user";
List<User> list=r.query(sql, new BeanListHandler<User>(User.class));
return list;
}


}

3.QueryRunner示例代码：单元测试增删改代码
单元测试增加数据：

package cn.itcast.jdbc.dao;
import java.sql.SQLException;

import org.junit.Test;

import cn.itcast.jdbc.javabean.User;

public class test {
@Test
			public void testInsert() throws SQLException {
			UserDaoQr dao=new UserDaoQr();
			User user=new User();
			user.setName("svdviming");
			user.setPassword("dad2dadadadad3");
			
			boolean b=dao.insert(user);
			
			if(b)
			System.out.println("数据插入成功！");
			else
			System.out.println("数据插入失败！");
			}
}
		单元测试删除数据：
@Test
public void testDelete() throws SQLException {
UserDaoQr dao=new UserDaoQr();
boolean b=dao.delete(3);
if(b)
System.out.println("数据删除成功！");
else
System.out.println("数据删除失败！");
}

}

测试结果：
数据删除成功！

4.QueryRunner示例代码：查询单个，并测试

package cn.itcast.jdbc.dao;

import java.sql.SQLException;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;


import cn.itcast.jdbc.javabean.User;
import cn.itcast.jdbc.utils.DataSourceUtils;

public class UserDaoQr {
	 public User find(int id) throws SQLException{
	     QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
	     String sql = "SELECT * FROM user WHERE id=?";
	     User user= r.query(sql, new BeanHandler<User>(User.class),id);
	     return user;
	  }

}

测试ID为2的数据：

package cn.itcast.jdbc.dao;

import java.sql.SQLException;

import org.junit.Test;

import cn.itcast.jdbc.javabean.User;

public class test {
	@Test
	public void testFind() throws SQLException {
	  UserDaoQr dao=new UserDaoQr();
	   User user=dao.find(2);
	   System.out.println("name="+user.getName());
	 }


}

测试结果：
成功查询ID=2的数据！

5.QueryRunner示例代码：查询全部，并测试

package cn.itcast.jdbc.dao;

import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;

import cn.itcast.jdbc.javabean.User;
import cn.itcast.jdbc.utils.DataSourceUtils;

public class UserDaoQr {
public List<User> findAll() throws SQLException{
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "SELECT * FROM user";
List<User> list=r.query(sql, new BeanListHandler<User>(User.class));
return list;
}
}

测试结果：
成功通过 findAll测试查询表中数据信息。