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SQL
String sql = "insert user values(null,'ddd','444','赵六')";
//执行SQL
int 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SQL
String sql = "update user set username='qqq',password='1234',name='或无言' where uid=4";
//执行SQL
int 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SQL
String sql = "delete from user where uid=4";
//执行SQL
int 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SQL
rs = 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;
}
}
}
}