jdbc入门
2.1 之前操作数据
1）通过mysql的客户端工具，登录数据库服务器 （mysql -u root -p 密码）
2）编写sql语句
3）发送sql语句到数据库服务器执行
2.2 什么是jdbc？
使用java代码（程序）发送sql语句的技术，就是jdbc技术！！！！
2.3 使用jdbc发送sql前提
登录数据库服务器（连接数据库服务器）
数据库的IP地址
端口
数据库用户名
密码
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/** * jdbc连接数据库 * @author APPle * */ public class Demo1 { //连接数据库的URL private String url = "jdbc:mysql://localhost:3306/day17"; // jdbc协议:数据库子协议:主机:端口/连接的数据库 // private String user = "root";//用户名 private String password = "root";//密码 /** * 第一种方法 * @throws Exception */ @Test public void test1() throws Exception{ //1.创建驱动程序类对象 Driver driver = new com.mysql.jdbc.Driver(); //新版本 //Driver driver = new org.gjt.mm.mysql.Driver(); //旧版本 //设置用户名和密码 Properties props = new Properties(); props.setProperty("user", user); props.setProperty("password", password); //2.连接数据库，返回连接对象 Connection conn = driver.connect(url, props); System.out.println(conn); } /** * 使用驱动管理器类连接数据库(注册了两次，没必要) * @throws Exception */ @Test public void test2() throws Exception{ Driver driver = new com.mysql.jdbc.Driver(); //Driver driver2 = new com.oracle.jdbc.Driver(); //1.注册驱动程序(可以注册多个驱动程序) DriverManager.registerDriver(driver); //DriverManager.registerDriver(driver2); //2.连接到具体的数据库 Connection conn = DriverManager.getConnection(url, user, password); System.out.println(conn); } /** * （推荐使用这种方式连接数据库） * 推荐使用加载驱动程序类 来 注册驱动程序 * @throws Exception */ @Test public void test3() throws Exception{ //Driver driver = new com.mysql.jdbc.Driver(); //通过得到字节码对象的方式加载静态代码块，从而注册驱动程序 Class.forName("com.mysql.jdbc.Driver"); //Driver driver2 = new com.oracle.jdbc.Driver(); //1.注册驱动程序(可以注册多个驱动程序) //DriverManager.registerDriver(driver); //DriverManager.registerDriver(driver2); //2.连接到具体的数据库 Connection conn = DriverManager.getConnection(url, user, password); System.out.println(conn); } } |
2.4 JDBC接口核心的API
java.sql.* 和 javax.sql.*
|- Driver接口： 表示java驱动程序接口。所有的具体的数据库厂商要来实现此接口。
|- connect(url, properties): 连接数据库的方法。
url: 连接数据库的URL
URL语法： jdbc协议:数据库子协议://主机:端口/数据库
user： 数据库的用户名
password： 数据库用户密码
|- DriverManager类： 驱动管理器类，用于管理所有注册的驱动程序
|-registerDriver(driver) : 注册驱动类对象
|-Connection getConnection(url,user,password); 获取连接对象
|- Connection接口： 表示java程序和数据库的连接对象。
|- Statement createStatement() ： 创建Statement对象
|- PreparedStatement prepareStatement(String sql) 创建PreparedStatement对象
|- CallableStatement prepareCall(String sql) 创建CallableStatement对象
|- Statement接口： 用于执行静态的sql语句
|- int executeUpdate(String sql) ： 执行静态的更新sql语句（DDL，DML）
|- ResultSet executeQuery(String sql) ：执行的静态的查询sql语句（DQL）
|-PreparedStatement接口：用于执行预编译sql语句
|- int executeUpdate() ： 执行预编译的更新sql语句（DDL，DML）
|-ResultSet executeQuery() ： 执行预编译的查询sql语句（DQL）
|-CallableStatement接口：用于执行存储过程的sql语句（call xxx）
|-ResultSet executeQuery() ： 调用存储过程的方法
|- ResultSet接口：用于封装查询出来的数据
|- boolean next() ： 将光标移动到下一行
|-getXX() : 获取列的值
3 使用Statement执行sql语句
3.1 执行DDL语句
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/** * 执行DDL语句(创建表) */ @Test public void test1(){ Statement stmt = null; Connection conn = null; try { //1.驱动注册程序 Class.forName("com.mysql.jdbc.Driver"); //2.获取连接对象 conn = DriverManager.getConnection(url, user, password); //3.创建Statement stmt = conn.createStatement(); //4.准备sql String sql = "CREATE TABLE student(id INT PRIMARY KEY AUTO_INCREMENT,NAME VARCHAR(20),gender VARCHAR(2))"; //5.发送sql语句，执行sql语句,得到返回结果 int count = stmt.executeUpdate(sql); //6.输出 System.out.println("影响了"+count+"行！"); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } finally{ //7.关闭连接(顺序:后打开的先关闭) if(stmt!=null) try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException(e); } if(conn!=null) try { conn.close(); } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException(e); } } } |
3.2 执行DML语句
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/** * 使用Statement执行DML语句 * @author APPle * */ public class Demo2 { private String url = "jdbc:mysql://localhost:3306/day17"; private String user = "root"; private String password = "root"; /** * 增加 */ @Test public void testInsert(){ Connection conn = null; Statement stmt = null; try { //通过工具类获取连接对象 conn = JdbcUtil.getConnection(); //3.创建Statement对象 stmt = conn.createStatement(); //4.sql语句 String sql = "INSERT INTO student(NAME,gender) VALUES('李四','女')"; //5.执行sql int count = stmt.executeUpdate(sql); System.out.println("影响了"+count+"行"); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } finally{ //关闭资源 /*if(stmt!=null) try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException(e); } if(conn!=null) try { conn.close(); } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException(e); }*/ JdbcUtil.close(conn, stmt); } } /** * 修改 */ @Test public void testUpdate(){ Connection conn = null; Statement stmt = null; //模拟用户输入 String name = "陈六"; int id = 3; try { /*//1.注册驱动 Class.forName("com.mysql.jdbc.Driver"); //2.获取连接对象 conn = DriverManager.getConnection(url, user, password);*/ //通过工具类获取连接对象 conn = JdbcUtil.getConnection(); //3.创建Statement对象 stmt = conn.createStatement(); //4.sql语句 String sql = "UPDATE student SET NAME='"+name+"' WHERE id="+id+""; System.out.println(sql); //5.执行sql int count = stmt.executeUpdate(sql); System.out.println("影响了"+count+"行"); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } finally{ //关闭资源 /*if(stmt!=null) try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException(e); } if(conn!=null) try { conn.close(); } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException(e); }*/ JdbcUtil.close(conn, stmt); } } /** * 删除 */ @Test public void testDelete(){ Connection conn = null; Statement stmt = null; //模拟用户输入 int id = 3; try { /*//1.注册驱动 Class.forName("com.mysql.jdbc.Driver"); //2.获取连接对象 conn = DriverManager.getConnection(url, user, password);*/ //通过工具类获取连接对象 conn = JdbcUtil.getConnection(); //3.创建Statement对象 stmt = conn.createStatement(); //4.sql语句 String sql = "DELETE FROM student WHERE id="+id+""; System.out.println(sql); //5.执行sql int count = stmt.executeUpdate(sql); System.out.println("影响了"+count+"行"); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } finally{ //关闭资源 /*if(stmt!=null) try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException(e); } if(conn!=null) try { conn.close(); } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException(e); }*/ JdbcUtil.close(conn, stmt); } } } |
3.3 执行DQL语句
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/** * 使用Statement执行DQL语句（查询操作） * @author APPle */ public class Demo3 { @Test public void test1(){ Connection conn = null; Statement stmt = null; try{ //获取连接 conn = JdbcUtil.getConnection(); //创建Statement stmt = conn.createStatement(); //准备sql String sql = "SELECT * FROM student"; //执行sql ResultSet rs = stmt.executeQuery(sql); //移动光标 /*boolean flag = rs.next(); flag = rs.next(); flag = rs.next(); if(flag){ //取出列值 //索引 int id = rs.getInt(1); String name = rs.getString(2); String gender = rs.getString(3); System.out.println(id+","+name+","+gender); //列名称 int id = rs.getInt("id"); String name = rs.getString("name"); String gender = rs.getString("gender"); System.out.println(id+","+name+","+gender); }*/ //遍历结果 while(rs.next()){ int id = rs.getInt("id"); String name = rs.getString("name"); String gender = rs.getString("gender"); System.out.println(id+","+name+","+gender); } }catch(Exception e){ e.printStackTrace(); throw new RuntimeException(e); }finally{ JdbcUtil.close(conn, stmt); } } } |
4 使用PreparedStatement执行sql语句
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public class Demo1 { /** * 增加 */ @Test public void testInsert() { Connection conn = null; PreparedStatement stmt = null; try { //1.获取连接 conn = JdbcUtil.getConnection(); //2.准备预编译的sql String sql = "INSERT INTO student(NAME,gender) VALUES(?,?)"; //?表示一个参数的占位符 //3.执行预编译sql语句(检查语法) stmt = conn.prepareStatement(sql); //4.设置参数值 /** * 参数一： 参数位置 从1开始 */ stmt.setString(1, "李四"); stmt.setString(2, "男"); //5.发送参数，执行sql int count = stmt.executeUpdate(); System.out.println("影响了"+count+"行"); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } finally { JdbcUtil.close(conn, stmt); } } /** * 修改 */ @Test public void testUpdate() { Connection conn = null; PreparedStatement stmt = null; try { //1.获取连接 conn = JdbcUtil.getConnection(); //2.准备预编译的sql String sql = "UPDATE student SET NAME=? WHERE id=?"; //?表示一个参数的占位符 //3.执行预编译sql语句(检查语法) stmt = conn.prepareStatement(sql); //4.设置参数值 /** * 参数一： 参数位置 从1开始 */ stmt.setString(1, "王五"); stmt.setInt(2, 9); //5.发送参数，执行sql int count = stmt.executeUpdate(); System.out.println("影响了"+count+"行"); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } finally { JdbcUtil.close(conn, stmt); } } /** * 删除 */ @Test public void testDelete() { Connection conn = null; PreparedStatement stmt = null; try { //1.获取连接 conn = JdbcUtil.getConnection(); //2.准备预编译的sql String sql = "DELETE FROM student WHERE id=?"; //?表示一个参数的占位符 //3.执行预编译sql语句(检查语法) stmt = conn.prepareStatement(sql); //4.设置参数值 /** * 参数一： 参数位置 从1开始 */ stmt.setInt(1, 9); //5.发送参数，执行sql int count = stmt.executeUpdate(); System.out.println("影响了"+count+"行"); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } finally { JdbcUtil.close(conn, stmt); } } /** * 查询 */ @Test public void testQuery() { Connection conn = null; PreparedStatement stmt = null; ResultSet rs = null; try { //1.获取连接 conn = JdbcUtil.getConnection(); //2.准备预编译的sql String sql = "SELECT * FROM student"; //3.预编译 stmt = conn.prepareStatement(sql); //4.执行sql rs = stmt.executeQuery(); //5.遍历rs while(rs.next()){ int id = rs.getInt("id"); String name = rs.getString("name"); String gender = rs.getString("gender"); System.out.println(id+","+name+","+gender); } } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } finally { //关闭资源 JdbcUtil.close(conn,stmt,rs); } } } |
PreparedStatement vs Statment
1）语法不同：PreparedStatement可以使用预编译的sql，而Statment只能使用静态的sql
2）效率不同： PreparedStatement可以使用sql缓存区，效率比Statment高
3）安全性不同： PreparedStatement可以有效防止sql注入，而Statment不能防止sql注入。
推荐使用PreparedStatement
5 CallableStatement执行存储过程
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/** * 使用CablleStatement调用存储过程 * @author APPle * */ public class Demo1 { /** * 调用带有输入参数的存储过程 * CALL pro_findById(4); */ @Test public void test1(){ Connection conn = null; CallableStatement stmt = null; ResultSet rs = null; try { //获取连接 conn = JdbcUtil.getConnection(); //准备sql String sql = "CALL pro_findById(?)"; //可以执行预编译的sql //预编译 stmt = conn.prepareCall(sql); //设置输入参数 stmt.setInt(1, 6); //发送参数 rs = stmt.executeQuery(); //注意： 所有调用存储过程的sql语句都是使用executeQuery方法执行！！！ //遍历结果 while(rs.next()){ int id = rs.getInt("id"); String name = rs.getString("name"); String gender = rs.getString("gender"); System.out.println(id+","+name+","+gender); } } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } finally { JdbcUtil.close(conn, stmt ,rs); } } /** * 执行带有输出参数的存储过程 * CALL pro_findById2(5,@NAME); */ @Test public void test2(){ Connection conn = null; CallableStatement stmt = null; ResultSet rs = null; try { //获取连接 conn = JdbcUtil.getConnection(); //准备sql String sql = "CALL pro_findById2(?,?)"; //第一个？是输入参数，第二个？是输出参数 //预编译 stmt = conn.prepareCall(sql); //设置输入参数 stmt.setInt(1, 6); //设置输出参数(注册输出参数) /** * 参数一： 参数位置 * 参数二： 存储过程中的输出参数的jdbc类型 VARCHAR(20) */ stmt.registerOutParameter(2, java.sql.Types.VARCHAR); //发送参数，执行 stmt.executeQuery(); //结果不是返回到结果集中，而是返回到输出参数中 //得到输出参数的值 /** * 索引值： 预编译sql中的输出参数的位置 */ String result = stmt.getString(2); //getXX方法专门用于获取存储过程中的输出参数 System.out.println(result); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } finally { JdbcUtil.close(conn, stmt ,rs); } } } |
MySqlUtil代码：
package com.sql.util; import java.io.FileInputStream; import java.io.InputStream; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.Properties; import javax.management.RuntimeErrorException; import com.mysql.jdbc.Driver; public class MysqlUtil { private static String url = null; private static String user = null; private static String password = null; private static String driverClass = null; static{ try { Properties properties = new Properties(); // FileInputStream fileInputStream = new FileInputStream("./src/db.properties"); InputStream in = MysqlUtil.class.getResourceAsStream("/db.properties"); properties.load(in); url = properties.getProperty("url"); user = properties.getProperty("user"); password = properties.getProperty("password"); driverClass = properties.getProperty("driverClass"); Class.forName(driverClass); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } public static Connection getConn() { // TODO Auto-generated method stub try { Connection conn = DriverManager.getConnection(url, user, password); return conn; } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); throw new RuntimeException(); } } public static void close(Connection conn, Statement state) { if(conn != null){ try { conn.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } if(state != null){ try { state.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } public static void close(Connection conn, Statement state, ResultSet resultSet) { if(resultSet != null){ try { resultSet.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); throw new RuntimeException(); } } if(conn != null){ try { conn.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } if(state != null){ try { state.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }
链接数据库练习：
import java.sql.Connection; import java.sql.DriverManager; import java.sql.DriverPropertyInfo; import java.sql.SQLException; import java.sql.SQLFeatureNotSupportedException; import java.sql.Statement; import java.util.Properties; import java.util.logging.Logger; import org.junit.Test; import com.mysql.jdbc.Driver; import com.sql.util.MysqlUtil; public class Connect { private String url = "jdbc:mysql://localhost:3306/handsomecui"; private String user = "root"; private String password = "123456"; public void test1() throws SQLException { Driver driver = new Driver(); Properties info = new Properties(); info.setProperty("user", user); info.setProperty("password", password); Connection connect = driver.connect(url, info); System.out.println(connect); } public void test2() throws Exception{ Class.forName("com.mysql.jdbc.Driver"); Connection conn = DriverManager.getConnection(url, user, password); System.out.println(conn); } public void test3() { Statement stat = null; Connection conn = null; try { Class.forName("com.mysql.jdbc.Driver"); conn = DriverManager.getConnection(url, user, password); stat = conn.createStatement(); String sql = "CREATE TABLE mystudent(id INT,NAME VARCHAR(20))"; int count = stat.executeUpdate(sql); System.out.println(count); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ if(stat != null){ try { stat.close(); } catch (SQLException e) { // TODO Auto-generated catch block throw new RuntimeException(); } } if(conn != null){ try { stat.close(); } catch (SQLException e) { // TODO Auto-generated catch block throw new RuntimeException(); } } } } @Test public void add() { Connection conn = null; Statement statement = null; try { conn = MysqlUtil.getConn(); statement = conn.createStatement(); String sql = "SELECT * FROM mystudent;"; int count = statement.executeUpdate(sql); System.out.println(count); } catch (Exception e) { // TODO: handle exception }finally{ MysqlUtil.close(conn, statement); } } }
查询语句简单练习：
import java.sql.CallableStatement; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import org.junit.Test; import com.sql.util.MysqlUtil; public class Query { public void test1() { Connection conn = null; PreparedStatement state = null; try { conn = MysqlUtil.getConn(); String sql = "insert into mystudent values(?,?)"; state = conn.prepareStatement(sql); state.setInt(1, 3); state.setString(2, "王五"); int count = state.executeUpdate(); System.out.println("影响了" + count + "行"); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); throw new RuntimeException(); }finally{ MysqlUtil.close(conn, state); } } public void test2() { // TODO Auto-generated method stub Connection conn = null; Statement state = null; ResultSet result = null; try { conn = MysqlUtil.getConn(); String sql = "SELECT * FROM mystudent;"; result = state.executeQuery(sql); while(result.next()){ System.out.println(result.getInt("id") + "," + result.getString("name")); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); throw new RuntimeException(); }finally{ MysqlUtil.close(conn, state, result); } } public void test3() { // TODO Auto-generated method stub Connection conn = null; CallableStatement state = null; ResultSet result = null; try { conn = MysqlUtil.getConn(); String sql = "CALL pro_query(?)"; state = conn.prepareCall(sql); state.setInt(1, 2); result = state.executeQuery(); while(result.next()){ System.out.println(result.getInt("id") + "," + result.getString("name")); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); throw new RuntimeException(); }finally{ MysqlUtil.close(conn, state, result); } } @Test public void test4() { Connection conn = null; CallableStatement state = null; ResultSet resultSet = null; try { conn = MysqlUtil.getConn(); String sql = "CALL findNameByid(?,?);"; state = conn.prepareCall(sql); state.setInt(1, 2); state.registerOutParameter(2, java.sql.Types.VARCHAR); state.executeQuery(); String result = state.getString(2); System.out.println(result); } catch (Exception e) { throw new RuntimeException(e); }finally{ MysqlUtil.close(conn, state); } } }