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

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 exceptione.printStackTrace();}finally {if(rs!=null) {try {rs.close();} catch (SQLException e) {// TODO: handle exceptione.printStackTrace();}rs=null;}if (stmt!=null) {try {stmt.close();} catch (SQLException e) {// TODO: handle exceptione.printStackTrace();}stmt=null;}if (conn!=null) {try {conn.close();} catch (SQLException e) {// TODO: handle exceptione.printStackTrace();}conn=null;}}}
}

结果如图

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

ResultSet对象

使用ResultSet对象取出指定数据的信息

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

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

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:

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:

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:

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。

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ResultSet对象

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