java之jdbc入门笔记2

注意导包：mysql-connector-java-5.1.39-bin.jar

配置文件：jdbc.properties(放在src下)

driverClass=com.mysql.jdbc.Driver

url=jdbc:mysql://localhost:3306/webstudy

user=root

password=123

jdbc的工具类

package jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ResourceBundle;

public class JdbcUtil {
//用于加载配置文件为properties快速的工具，避免繁杂的IO操作
static ResourceBundle bundle;
static String url;
static String user;
static String password;
static{
bundle = ResourceBundle.getBundle("jdbc");
url = bundle.getString("url");
user= bundle.getString("user");
password= bundle.getString("password");

try {
//加载驱动
Class.forName(bundle.getString("driverClass"));
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/**
* 获取连接
* */
public static Connection getConnection(){
try {
return DriverManager.getConnection(url, user, password);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
}
/**
* 关闭资源
* */
public static void closeResource(Connection conn,PreparedStatement stm,ResultSet rs){
if(rs!=null){
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
rs=null;
}
}
if(stm!=null){
try {
stm.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
stm=null;
}
}
if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
conn=null;
}
}
}

}


jdbc案例：curd

package jdbc;

import java.sql.Connection;
import java.sql.PreparedStatement;

import java.sql.ResultSet;

import org.junit.After;
import org.junit.Test;
/**
* 数据库的curd
* */
public class JdbcTest {
@Test
public void read(){
Connection conn;
PreparedStatement stm;
ResultSet rs;
try {
conn = JdbcUtil.getConnection();
String sql = "select * from t_user";
stm=conn.prepareStatement(sql);
rs=stm.executeQuery();
while(rs.next()){
//通过数据库字段名获取值
System.out.println("cid:"+rs.getInt("uid")+" username:"+rs.getString("username"));
}
JdbcUtil.closeResource(conn, stm, rs);
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
@Test
public void update(){
Connection conn;
PreparedStatement stm;
int rs;
try {
conn = JdbcUtil.getConnection();
String sql = "insert into t_user values(?,?)";
stm=conn.prepareStatement(sql);
//设置sql中的参数
stm.setInt(1, 3);
stm.setString(2, "芈月");
rs = stm.executeUpdate();//返回数据执行操作后的影响行数，插入成功返回大于0的数
if(rs>0){
System.out.println("success");
}else{
System.out.println("false");
}
JdbcUtil.closeResource(conn, stm, null);
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
@Test
public void change(){
Connection conn;
PreparedStatement stm;
int rs;
try {
conn = JdbcUtil.getConnection();
String sql = "update t_user set username=? where uid=?";
stm=conn.prepareStatement(sql);
stm.setInt(2, 3);
stm.setString(1, "宫本");
rs = stm.executeUpdate();//返回数据执行操作后的影响行数。
if(rs>0){
System.out.println("success");
}else{
System.out.println("false");
}
JdbcUtil.closeResource(conn, stm, null);
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
@Test
public void delete(){
Connection conn;
PreparedStatement stm;
int rs;
try {
conn = JdbcUtil.getConnection();
String sql = "delete from t_user where uid=?";
stm=conn.prepareStatement(sql);
stm.setInt(1, 3);
rs = stm.executeUpdate();//返回数据执行操作后的影响行数。
if(rs>0){
System.out.println("success");
}else{
System.out.println("false");
}
JdbcUtil.closeResource(conn, stm, null);
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}

}