[大数据]JavaWeb JDBC

1.实现第一个JDBC程序

在MySQL中创建一个名称为jdbc的数据库，然后在该数据库中创建一个users表，创建
数据库和表的SQL语句如下所示。

 CREATE DATABASE jdbc;
 USE jdbc;
 
 CREATE TABLE users(
   id INT PRIMARY KEY AUTO_INCREMENT,
   name VARCHAR(40),
   password VARCHAR(40),
   email VARCHAR(60),
   birthday DATE
   )CHARACTER SET utf8 COLLATE utf8_general_ci;

数据库和表创建成功后,创建插入记录:

INSERT INTO users (NAME, PASSWORD, email, birthday)
VALUES('zs', '123456','zs@sina.com','1980-12-04');
INSERT INTO users (NAME, PASSWORD, email,birthday)
VALUES('lisi','123456','lisi0sina.com','1981-12-04');
INSERT INTO users (NAME, PASSWORD, email,birthday)
VALUES('wangwu','123456','wangwu@sina.com','1979-12-04');

执行结果如图

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2.编写JDBC程序

在项目chapter09的src目录下，新建一个名称为chapter02.jdbc.example的包，在该包中创建类Example01，该类用于读取数据库中的users表，并将结果输出到控制台

package chapter12.jdbc.example;

import java.sql.Statement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;

public class example01 {
	public static void main(String[] args) throws SQLException{
		Connection conn = null;
		Statement stmt = null;
		ResultSet rs  = null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			String url = "jdbc:mysql://localhost:3306/jdbc?serverTimezone=UTC";
			String username = "root";
			String password = "123456";
			conn = DriverManager.getConnection(url,username,password);
			stmt = conn.createStatement();
			String sql = "select * from users";
			rs = stmt.executeQuery(sql);
			while (rs.next()) {
				int id = rs.getInt("id");
				String name = rs.getString("name");
				String psw = rs.getString("password");
				String email = rs.getString("email");
				Date birthday = rs.getDate("birthday");
				System.out.println(id+" "+name+" "+email+" "+birthday);
			}
		}catch (ClassNotFoundException e) {
			// TODO: handle exception
			e.printStackTrace();
		}finally {
			if(rs!=null) {
				try {
					rs.close();
				} catch (SQLException e) {
					// TODO: handle exception
					e.printStackTrace();
				}
				rs=null;
			}
			if (stmt!=null) {
				try {
					stmt.close();
				} catch (SQLException e) {
					// TODO: handle exception
					e.printStackTrace();
				}
				stmt=null;
			}
			if (conn!=null) {
				try {
					conn.close();
				} catch (SQLException e) {
					// TODO: handle exception
					e.printStackTrace();
				}
				conn=null;
			}
		}
	}
}

结果如图

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PreparedStatement对象

在该类中使用PreparedStatement对象对数据库进行插入数据的操作

package chapter12.jdbc.example;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
 
public class example02 {
	public static void main(String[] args) throws SQLException{
		Connection conn = null;
		PreparedStatement preStmt = null;
		try {
			Class.forName("com.mysql.cj.jdbc.Driver");
			String url = "jdbc:mysql://localhost:3306/jdbc?serverTimezone=UTC";
			String username = "root";
			String password = "123456";
			conn = DriverManager.getConnection(url,username,password); 
			String sql ="INSERT INTO users (NAME, PASSWORD, email,birthday)"+"VALUES(?,?,?,?)";
			preStmt =conn.prepareStatement(sql);
			preStmt.setString(1, "zl");
			preStmt.setString(2, "123456");
			preStmt.setString(3, "zl@sina.com");
			preStmt.setString(4, "1789-12-23");
			preStmt.executeUpdate();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} finally {
			if(preStmt!=null) {
				try {
					preStmt.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
				preStmt = null;
			}
			if(conn!=null) {
				try {
					conn.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
				conn=null;
			}
		}
	}
}

查询结果如图

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ResultSet对象

使用ResultSet对象取出指定数据的信息

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package chapter12.jdbc.example;


	import java.sql.Connection;
	import java.sql.DriverManager;
	import java.sql.ResultSet;
	import java.sql.SQLException;
	import java.sql.Statement;
	 
	public class example03 {
		public static void main(String[] args) {
			Connection conn = null;
			Statement stmt = null;
			try {
				Class.forName("com.mysql.cj.jdbc.Driver");
				String url = "jdbc:mysql://localhost:3306/jdbc?serverTimezone=UTC";
				String username = "root";
				String password = "123456";
				conn = DriverManager.getConnection(url,username,password);
				String sql = "select * from users";
				stmt = conn.createStatement(
						ResultSet.TYPE_SCROLL_INSENSITIVE,
						ResultSet.CONCUR_READ_ONLY);
				ResultSet rs = stmt.executeQuery(sql);
				System.out.print("第2条数据的name值为：");
				rs.absolute(2);
				System.out.println(rs.getNString("name"));
				System.out.print("第1条数据的name值为：");
				rs.beforeFirst();  //将指针定位到结果集中第一行数据之前
				rs.next();	//指针向后滚动
				System.out.println(rs.getString("name"));
				System.out.print("第4条数据的name值为：");
				rs.afterLast(); //将指针定位到结果集中最后一条数据之后
				rs.previous();	//指针向前滚动
				System.out.println(rs.getString("name"));
			} catch (Exception e) {
				e.printStackTrace();
			} finally {
				if(stmt!=null) {
					try {
						stmt.close();
					} catch (SQLException e) {
						e.printStackTrace();
					}
					stmt = null;
				}
				if(conn!=null) {
					try {
						conn.close();
					} catch (SQLException e) {
						e.printStackTrace();
					}
					conn=null;
				}
			}
		}
}

程序的运行结果如图?

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使用JDBC完成数据的增删改查

1.创建JavaBean

User类的具体实现方式如下

package chapter12.jdbc.example;

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;
	}

2.创建工具类

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，下面建立一个专门用于数据库相关操作的工具类。在包中创建一个封装了上述操作的工具类JDBCUtils，JDBCUtils的具体实现方式如下

package chapter12.jdbc.example;

	import java.sql.Connection;
	import java.sql.DriverManager;
	import java.sql.ResultSet;
	import java.sql.SQLException;
	import java.sql.Statement;
	 
	public class JDBCUtils {
		public static Connection getConnection() throws SQLException,ClassNotFoundException{
				Class.forName("com.mysql.cj.jdbc.Driver");
				String url = "jdbc:mysql://localhost:3306/jdbc?serverTimezone=UTC";
				String username = "root";
				String password = "123456";
				Connection conn = DriverManager.getConnection(url,username,password);
				return conn;
		}
		public static void release(Statement stmt, Connection conn) {
			if(stmt!=null) {
				try {
					stmt.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
				stmt = null;
			}
			if(conn!=null) {
				try {
					conn.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
				conn=null;
			}
		}
		public static void release(ResultSet rs,Statement stmt,Connection conn) {
			if(rs!=null) {
				try {
					rs.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
				rs = null;
			}
			release(stmt, conn);
		}
	}

3.创建DAO

代码如下:

package chapter12.jdbc.example;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
 
import chapter12.jdbc.example.user;
import chapter12.jdbc.example.JDBCUtils;
 
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 users(id,name,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 users";
			rs = stmt.executeQuery(sql);
			while(rs.next()) {
				user user = new user();
				user.setId(rs.getInt("id"));
				user.setUsername(rs.getString("name"));
				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 users WHERE id=" + id;
			rs = stmt.executeQuery(sql);
			while(rs.next()) {
				user user = new user();
				user.setId(rs.getInt("id"));
				user.setUsername(rs.getString("name"));
				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 users 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 users set name='"+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.创建测试类

代码如下:

package chapter12.jdbc.example;

import java.util.Date;
import chapter12.jdbc.example.user;
import chapter12.jdbc.example.JDBCUtils;
 
public class JdbcInsertTest {
	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(5);
		user.setUsername("hl");
		user.setPassword("123");
		user.setEmail("hl@sina.com");
		user.setBirthday(new Date());
		boolean b= ud.insert(user);
		System.out.println(b);
	}

}

结果如图

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从查询结果可以看出，users表中添加了一条name为h1的数据，该数据正是文件 JdbclnsertTest.java中所插入的数据。

?编写测试类FindAllUsersTest,该类用于实现读取users表中所有的数据:

package chapter12.jdbc.example;

import java.util.ArrayList;

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());
		}
	}

}

结果如图:

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编写测试类FindUserByldTest,在该类中实现读取 users表中指定的数据:

package chapter12.jdbc.example;
import chapter12.jdbc.example.UsersDao;
import chapter12.jdbc.example.user;
 
public class FindUserByldTest {
	public static void main(String[] args) {
		UsersDao usersDao = new UsersDao();
		user user = usersDao.find(1);
		System.out.println("id为1的User对象的name值为："+user.getUsername());
	}

}

结果如图:

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编写测试类UpdateUserTest,在该类中实现修改users表中数据的操作:

package chapter12.jdbc.example;

import java.util.Date;

import chapter12.jdbc.example.UsersDao;
import chapter12.jdbc.example.user;
 
public class UpdateUserTest {
	public static void main(String[] args) {
		UsersDao usersDao = new UsersDao();
		user user = new user();
		user.setId(4);
		user.setUsername("zhaoxiaoliu");
		user.setPassword("456");
		user.setEmail("zhaoxiaoliu@sina.com");
		user.setBirthday(new Date());
		boolean b=usersDao.update(user);
		System.out.println(b);
	}

}

查询结果如图:

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编写测试类DeleteUserTest,该类实现了删除users 表中数据的操作:

package chapter12.jdbc.example;

import chapter12.jdbc.example.UsersDao;

public class DeleteUserTest {
	public static void main(String[] args) {
		UsersDao usersDao = new UsersDao();
		boolean b = usersDao.delete(4);
		System.out.println(b);
	}

}

?结果如图:

从图中可以看出，users表中id为4的User对象已被成功删除了。至此，使用JDBC对数据库中数据进行增删改查的操作已经完成。