本blog提供了一个简单的通过JDBC驱动建立JDBC连接例程,并分别通过Statement和PreparedStatement实现对数据库的查询。在下一篇blog中将重点比较Statement与PreparedStatement的差异。
1、为项目添加JDBC驱动
1)JDBC驱动下载
官方下载地址:mysql-connector-java-5.0.8.zip
CSDN资料下载地址:mysql-connector-java-5.0.8.zip
2)为项目添加JDBC驱动
建立项目Java项目JDBCDemo,并在JDBCDemo项目中建立一个lib文件夹,将驱动文件拷贝到lib文件夹,选中驱动文件,右键->BuildPath->Add To Build Path;如图所示:
2、建立db_bbs数据库
1)构建一个数据库db_bbs;
2)执行db_bbs.sql文件的sql语句,在db_bbs数据库中创建user表,并添加数据;
SET FOREIGN_KEY_CHECKS=0; -- ---------------------------- -- Table structure for `user` -- ---------------------------- DROP TABLE IF EXISTS `user`; CREATE TABLE `user` ( `id` int(11) NOT NULL AUTO_INCREMENT, `username` varchar(10) NOT NULL, `password` varchar(10) NOT NULL, `gender` varchar(1) NOT NULL, `regtime` datetime NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=gb2312; -- ---------------------------- -- Records of user -- ---------------------------- INSERT INTO `user` VALUES (‘1‘, ‘andy‘, ‘andy‘, ‘1‘, ‘2014-05-13 17:33:28‘); INSERT INTO `user` VALUES (‘2‘, ‘jack‘, ‘jack‘, ‘1‘, ‘2014-05-14 17:33:55‘); INSERT INTO `user` VALUES (‘3‘, ‘rose‘, ‘rose‘, ‘0‘, ‘2014-05-13 17:34:36‘);
3、通过属性文件配置数据库
1)属性配置文件db.properties;
#mysql DB properties DB_DRIVER_CLASS=com.mysql.jdbc.Driver DB_URL=jdbc:mysql://localhost:3306/db_bbs DB_USERNAME=root DB_PASSWORD=root #Oracle DB Properties #DB_DRIVER_CLASS=oracle.jdbc.driver.OracleDriver #DB_URL=jdbc:oracle:thin:@localhost:1571:db_bbs #DB_USERNAME=scott #DB_PASSWORD=tiger
2)将属性配置文件添加到项目的根目录;
4、建立JDBC连接
package com.andieguo.jdbc; import java.io.FileInputStream; import java.io.IOException; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.Properties; /** * 该类封装了连接和关闭数据库连接操作 * * @author andieguo * */ public class DBConnection { public static Connection getConnection() { Properties props = new Properties(); FileInputStream fis = null; Connection con = null; try { fis = new FileInputStream("db.properties"); props.load(fis); // 加载驱动 Class.forName(props.getProperty("DB_DRIVER_CLASS")); // 创建一个连接 con = DriverManager.getConnection(props.getProperty("DB_URL"), props.getProperty("DB_USERNAME"), props.getProperty("DB_PASSWORD")); } catch (IOException | SQLException | ClassNotFoundException e) { e.printStackTrace(); } return con; } // 关闭ResultSet public static void closeResultSet(ResultSet rs) { if (rs != null) { try { rs.close(); rs = null; } catch (SQLException e) { e.printStackTrace(); } } } // 关闭Statement public static void closeStatement(Statement stm) { if (stm != null) { try { stm.close(); stm = null; } catch (SQLException e) { e.printStackTrace(); } } } // 关闭PreparedStatement public static void closePreparedStatement(PreparedStatement pstm) { if (pstm != null) { try { pstm.close(); pstm = null; } catch (SQLException e) { e.printStackTrace(); } } } // 关闭Connection public static void closeConnection(Connection con) { if (con != null) { try { con.close(); con = null; } catch (SQLException e) { e.printStackTrace(); } con = null; } } }
5、使用Statement进行查询
package com.andieguo.jdbc; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.List; public class DBHelper { public static void queryAllByStatement() { List<User> users = new ArrayList<User>(); Connection conn = DBConnection.getConnection(); Statement stmt = null; ResultSet rs = null; try { stmt = conn.createStatement(); rs = stmt.executeQuery("select * from user"); while (rs.next()) { User user = new User(); user.setId(rs.getInt("id")); user.setUsername(rs.getString("username")); user.setPassword(rs.getString("password")); user.setGender(rs.getBoolean("gender")); user.setRegtime(rs.getDate("regtime")); System.out.println(user.toString()); users.add(user); } } catch (SQLException e) { e.printStackTrace(); } finally { DBConnection.closeResultSet(rs); DBConnection.closeStatement(stmt); DBConnection.closeConnection(conn); } } public static void queryById(Integer id) { Connection conn = DBConnection.getConnection(); Statement stmt = null; ResultSet rs = null; try { stmt = conn.createStatement(); rs = stmt.executeQuery("select * from user where id = " + id); while (rs.next()) { User user = new User(); user.setId(rs.getInt("id")); user.setUsername(rs.getString("username")); user.setPassword(rs.getString("password")); user.setGender(rs.getBoolean("gender")); user.setRegtime(rs.getDate("regtime")); System.out.println(user.toString()); } } catch (SQLException e) { e.printStackTrace(); } finally { DBConnection.closeResultSet(rs); DBConnection.closeStatement(stmt); DBConnection.closeConnection(conn); } } }
6、使用PreparedStatement进行查询
package com.andieguo.jdbc; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; public class DBHelper { public static void queryAllByprepareStatement() { List<User> users = new ArrayList<User>(); Connection conn = DBConnection.getConnection(); PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement("select * from user"); rs = ps.executeQuery(); while (rs.next()) { User user = new User(); user.setId(rs.getInt("id")); user.setUsername(rs.getString("username")); user.setPassword(rs.getString("password")); user.setGender(rs.getBoolean("gender")); user.setRegtime(rs.getDate("regtime")); System.out.println(user.toString()); users.add(user); } } catch (SQLException e) { e.printStackTrace(); } finally { DBConnection.closeResultSet(rs); DBConnection.closeStatement(ps); DBConnection.closeConnection(conn); } } public static void queryPrepareById(Integer id) { Connection conn = DBConnection.getConnection(); PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement("select * from user where id = ?"); ps.setInt(1, id);// 设置占位符参数 rs = ps.executeQuery(); while (rs.next()) { User user = new User(); user.setId(rs.getInt("id")); user.setUsername(rs.getString("username")); user.setPassword(rs.getString("password")); user.setGender(rs.getBoolean("gender")); user.setRegtime(rs.getDate("regtime")); System.out.println(user.toString()); } } catch (SQLException e) { e.printStackTrace(); } finally { DBConnection.closeResultSet(rs); DBConnection.closeStatement(ps); DBConnection.closeConnection(conn); } } }
7、测试用例
package com.andieguo.jdbc; import junit.framework.TestCase; public class DBHelperTest extends TestCase { public void getConnectionTest(){ System.out.println(DBConnection.getConnection()); } public void queryAllByStatementTest(){ DBHelper.queryAllByStatement(); } public void queryAllByprepareStatementTest(){ DBHelper.queryAllByprepareStatement(); } public void queryByIdTest(){ DBHelper.queryById(2); } public void queryByPrepareIdTest(){ DBHelper.queryPrepareById(3); } }
8、参考
JDBC Example Tutorial – Drivers, Connection, Statement and ResultSet(推荐)
Java code for connecting Mysql database and using Arraylist type
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【Java编程】建立一个简单的JDBC连接-Drivers, Connection, Statement and PreparedStatement
时间: 2024-10-26 11:52:24