【JDBC】CRUD操作

JDBC的CRUD操作

  • 向数据库中保存记录
  • 修改数据库中的记录
  • 删除数据库中的记录
  • 查询数据库中的记录

保存代码的实现

package demo1;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.sql.Statement;import org.junit.Test;public class JDBCDemo3 {@Test/** * 保存代码的实现 */public void demo3() {Connection conn = null;Statement stmt = null;try {//注册驱动Class.forName("com.mysql.cj.jdbc.Driver");//获得连接conn = DriverManager.getConnection("jdbc:mysql:///jdbctest?serverTimezone=Hongkong", "root", "1234");//获得执行SQL语句的对象stmt = conn.createStatement();//编写SQLString sql = "insert user values(null,'ddd','444','赵六')";//执行SQLint i = stmt.executeUpdate(sql);if(i > 0) {System.out.println("保存成功！");}}catch(Exception e) {e.printStackTrace();}finally{//释放资源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;}}}}

修改代码的实现

package demo1;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.sql.Statement;import org.junit.Test;public class JDBCDemo3 {@Test/** * 修改代码的实现 */public void demo2() {Connection conn = null;Statement stmt = null;try {//注册驱动Class.forName("com.mysql.cj.jdbc.Driver");//获得连接conn = DriverManager.getConnection("jdbc:mysql:///jdbctest?serverTimezone=Hongkong", "root", "1234");//获得执行SQL语句的对象stmt = conn.createStatement();//编写SQLString sql = "update user set username='qqq',password='1234',name='或无言' where uid=4";//执行SQLint i = stmt.executeUpdate(sql);if(i > 0) {System.out.println("修改成功！");}}catch(Exception e) {e.printStackTrace();}finally{//释放资源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;}}}}

删除代码的实现

package demo1;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.sql.Statement;import org.junit.Test;public class JDBCDemo3 {@Test/** * 删除代码的实现 */public void demo1() {Connection conn = null;Statement stmt = null;try {//注册驱动Class.forName("com.mysql.cj.jdbc.Driver");//获得连接conn = DriverManager.getConnection("jdbc:mysql:///jdbctest?serverTimezone=Hongkong", "root", "1234");//获得执行SQL语句的对象stmt = conn.createStatement();//编写SQLString sql = "delete from user where uid=4";//执行SQLint i = stmt.executeUpdate(sql);if(i > 0) {System.out.println("删除成功！");}}catch(Exception e) {e.printStackTrace();}finally{//释放资源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;}}}}

查询代码的实现

package demo1;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import org.junit.Test;public class JDBCDemo1 {@Test/** * 查询代码的实现 */public void demo1() {Connection conn = null;Statement stmt = null;ResultSet rs = null;try {//1.加载驱动Class.forName("com.mysql.cj.jdbc.Driver");//2.获得连接conn = DriverManager.getConnection("jdbc:mysql:///jdbctest?serverTimezone=Hongkong", "root", "1234");//3创建执行SQL语句的对象，并且执行SQL//3.1创建执行SQL语句的对象String sql = "select * from user";stmt = conn.createStatement();//3.2执行SQLrs = stmt.executeQuery(sql);while(rs.next()) {int uid = rs.getInt("uid");String username = rs.getString("username");String password = rs.getString("password");String name = rs.getString("name");System.out.println(uid + "-" + username + "-" + password + "-" + name);}} catch (Exception e) {e.printStackTrace();} finally {//释放资源if(rs != null) {try {rs.close();} catch (SQLException e) {e.printStackTrace();}rs = null;}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;}}}}
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