JDBC、DBUtils

JDBC(Java Data Base Connectivity) java数据连接

可以为多种数据库，提供统一访问，它由一组用java语言编写的类和接口组成，也是java访问数据库的规范。

 

mysql数据库驱动程序jar包

http://dev.mysql.com/downloads/connector/

选 connector/j/ 下载

 

导入mysql数据库驱动程序jar包

file->project structure->modules->添加 jars or directories ->选择目标.jar

 

增删改 executeUpdate

String driverName = "com.mysql.jdbc.Driver";

//数据库地址 jdbc:mysql://主机IP:端口号/数据库名字

String url = "jdbc:mysql://localhost:3306/david2018_db";

String user = "root";

String password = "1234";

try {

//1.注册驱动

Class.forName(driverName);

 

//2.连接数据库

Connection conn = DriverManager.getConnection(url, user, password);

 

//3.获得执行对象

Statement stat = conn.createStatement();

 

//4.执行insert语句

String sql = "insert into users (uname,uaddress,tel) values ('baidawei','changpingqu','18755488125')";

int result = stat.executeUpdate(sql);

 

System.out.println("插入"+result+"条数据");

 

//5.释放资源

stat.close();

conn.close();

 

} catch (ClassNotFoundException e) {

e.printStackTrace();

} catch (SQLException e) {

e.printStackTrace();

}

 

查询数据 executeQuery

String driverName = "com.mysql.jdbc.Driver";

//数据库地址 jdbc:mysql://主机IP:端口号/数据库名字

String url = "jdbc:mysql://localhost:3306/david2018_db";

String user = "root";

String password = "1234";

try {

//1.注册驱动

Class.forName(driverName);

 

//2.连接数据库

Connection conn = DriverManager.getConnection(url, user, password);

 

//3.获得执行对象

Statement stat = conn.createStatement();

 

//4.执行select语句

String sql = "select * from users";

ResultSet rs = stat.executeQuery(sql);

while(rs.next()){

System.out.print(rs.getInt("uid"));

System.out.print(rs.getString("uname"));

System.out.println(rs.getString("uaddress"));

}

 

//5.释放资源

rs.close();

stat.close();

conn.close();

 

} catch (ClassNotFoundException e) {

e.printStackTrace();

} catch (SQLException e) {

e.printStackTrace();

}

}

 

PrepareStatement预编译 防 or 1=1 sql注入

String driverName = "com.mysql.jdbc.Driver";

//数据库地址 jdbc:mysql://主机IP:端口号/数据库名字

String url = "jdbc:mysql://localhost:3306/david2018_db";

String user = "root";

String password = "1234";

try {

//1.注册驱动

Class.forName(driverName);

 

//2.连接数据库

Connection conn = DriverManager.getConnection(url, user, password);

 

//3.获得执行对象

Statement stat = conn.createStatement();

 

//4.执行select语句

//String id = "5";

//String sql = "select * from users where uid > " + id;

String sql = "select * from users where uid > ?";

PreparedStatement pst = conn.prepareStatement(sql);

pst.setObject(1,5); //从1开始

ResultSet rs = pst.executeQuery(); //这里是pst的executeQuery()无参方法

while(rs.next()){

System.out.print(rs.getInt("uid"));

System.out.print(rs.getString("uname"));

System.out.println(rs.getString("uaddress"));

}

 

//5.释放资源

rs.close();

stat.close();

conn.close();

 

} catch (ClassNotFoundException e) {

e.printStackTrace();

} catch (SQLException e) {

e.printStackTrace();

}

 

修改操作

//4.执行update语句

String sql = "update users set uname = ? where uid = ?";

PreparedStatement pst = conn.prepareStatement(sql);

pst.setObject(1,"david");

pst.setObject(2,7);

 

int result = pst.executeUpdate();

System.out.println(result);

 

封装JDBCUtils工具类

import java.sql.*;

 

public class JDBCUtils {

private JDBCUtils(){}

 

private static Connection con ;

static{

try{

String driverName = "com.mysql.jdbc.Driver";

//数据库地址 jdbc:mysql://主机IP:端口号/数据库名字

String url = "jdbc:mysql://localhost:3306/david2018_db";

String user = "root";

String password = "1234";

//1.注册驱动

Class.forName(driverName);

 

//2.连接数据库

con = DriverManager.getConnection(url, user, password);

 

}catch(Exception ex){

throw new RuntimeException(ex+"数据库连接失败");

}

}

 

public static Connection getConnection(){

return con;

}

 

public static void close(Connection con,Statement stat){

 

if(stat!=null){

try{

stat.close();

}catch(SQLException ex){}

}

 

if(con!=null){

try{

con.close();

}catch(SQLException ex){}

}

 

}

 

public static void close(Connection con,Statement stat , ResultSet rs){

if(rs!=null){

try{

rs.close();

}catch(SQLException ex){}

}

 

if(stat!=null){

try{

stat.close();

}catch(SQLException ex){}

}

 

if(con!=null){

try{

con.close();

}catch(SQLException ex){}

}

 

}

}

 

测试工具类

public static void main(String[] args) {

Connection con = JDBCUtils.getConnection();

PreparedStatement pst = null;

try {

pst = con.prepareStatement("select * from users");

 

ResultSet rs = pst.executeQuery();

List<users> list = new ArrayList<users>();

while (rs.next()) {

users u = new users();

u.uid = rs.getInt("uid");

u.uname = rs.getString("uname");

u.uaddress = rs.getString("uaddress");

u.utel=rs.getString("tel");

list.add(u);

}

for(users u : list){

System.out.println(u.toString());

}

JDBCUtils.close(con, pst, rs);

} catch (SQLException e) {

e.printStackTrace();

}

}

 

配置文件

src目录下新建database.properties文件

driverName=com.mysql.jdbc.Driver

url=jdbc:mysql://localhost:3306/david2018_db

user=root

password=1234

 

加载配置文件

//类加载器

InputStream in = 当前类名.class.getClassLoader().getResourceAsStream("database.properties");

 

Properties pro = new Properties();

pro.load(in);

 

String driverName = pro.getProperty("driverName");

String url = pro.getProperty("url");

String user = pro.getProperty("user");

String password = pro.getProperty("password");

 

连接mysql方法

import java.io.InputStream;

import java.sql.Connection;

import java.sql.DriverManager;

import java.util.Properties;

 

public class JDBCUtilsConfig {

private static Connection con;

 

static {

InputStream in = JDBCUtilsConfig.class.getClassLoader().getResourceAsStream("database.properties");

 

Properties pro = new Properties();

try {

pro.load(in);

 

String driverName = pro.getProperty("driverName");

String url = pro.getProperty("url");

String user = pro.getProperty("user");

String password = pro.getProperty("password");

 

Class.forName(driverName);

con = DriverManager.getConnection(url, user, password);

} catch (Exception e) {

e.printStackTrace();

}

}

 

public static Connection getCon() {

return con;

}

}

 

DBUtils

简化JDBC开发

下载DBUtils jar包

http://commons.apache.org/proper/commons-dbutils/download_dbutils.cgi

command+; 导入jar包

 

QueryRunner.update 增删改

新增：

Connection con = JDBCUtilsConfig.getCon();

QueryRunner qr = new QueryRunner();

String sql = "insert into users (uname,uaddress,tel) values (?,?,?)";

Object[] params = {"davidddd","bj","15156156156156"};

int result = qr.update(con,sql,params);

System.out.println("添加"+result+"条数据");

DbUtils.closeQuietly(con);

 

修改：

Connection con = JDBCUtilsConfig.getCon();

QueryRunner qr = new QueryRunner();

String sql = "update users set uname = ?,uaddress = ? where uid = ?";

Object[] params = {"david1","sh",8};

int result = qr.update(con,sql,params);

System.out.println("修改"+result+"条数据");

DbUtils.closeQuietly(con);

 

删除：

Connection con = JDBCUtilsConfig.getCon();

QueryRunner qr = new QueryRunner();

String sql = "delete from users where uid = ?";

int result = qr.update(con,sql,8);

System.out.println("删除"+result+"条数据");

DbUtils.closeQuietly(con);

 

QueryRunner.query 查询

查询：

ArrayHandler 返回第一行Object[]

ArrayListHandler 返回List<Object[]>

Connection con = JDBCUtilsConfig.getCon();

QueryRunner qr = new QueryRunner();

String sql = "select * from users where uid > ?";

List<Object[]> result = qr.query(con,sql,new ArrayListHandler(),1);

for(Object[] obj : result){

for(Object o : obj){

System.out.println(o);

}

}

DbUtils.closeQuietly(con);

 

BeanHandler 返回第一行JavaBean对象

BeanListHandler 返回List JavaBean对象

Connection con = JDBCUtilsConfig.getCon();

QueryRunner qr = new QueryRunner();

String sql = "select * from users where uid > ?";

List<users> result = qr.query(con,sql,new BeanListHandler<users>(users.class),1);

for(users u : result){

System.out.println(u);

}

DbUtils.closeQuietly(con);

 

ColumnListHandler 返回List Object对象 按列查询

ScalarHandler 返回第一条数据 适合count

Connection con = JDBCUtilsConfig.getCon();

QueryRunner qr = new QueryRunner();

String sql = "select count(*) from users where uid > ?";

Long count = qr.query(con,sql,new ScalarHandler<Long>(),1);

System.out.println(count);

DbUtils.closeQuietly(con);

 

MapHandler 返回第一个Map对象 key value

MapListHandler 返回ListMap对象

Connection con = JDBCUtilsConfig.getCon();

QueryRunner qr = new QueryRunner();

String sql = "select * from users where uid > ?";

List<Map<String, Object>> result = qr.query(con,sql,new MapListHandler(),1);

for(Map<String,Object> map : result){

System.out.println(map.get("uid"));

}

DbUtils.closeQuietly(con);

 

连接池

共享Connection，避免频繁创建连接、释放连接操作。

用连接池来管理Connection，可以重复使用COnnection，不用我们自己创建Connection，

通过连接池来创建Connection对象，关闭也不会真正的关闭连接，而是吧Connection归还给它，连接池就可以再利用这个对象了。

DBCP

数据库连接池是apache上的一个Java连接池项目，DBCP所依赖的jar包

dbcp.jar poll.jar logging.jar 这三个jar包

http://commons.apache.org/proper/commons-dbcp/download_dbcp.cgi

http://commons.apache.org/proper/commons-pool/download_pool.cgi

http://commons.apache.org/proper/commons-logging/download_logging.cgi

导入jar包 command+;

 

BasicDataSource dataSource = new BasicDataSource();

dataSource.setDriverClassName("com.mysql.jdbc.Driver");

dataSource.setUrl("jdbc:mysql://localhost:3306/david2018_db");

dataSource.setUsername("root");

dataSource.setPassword("1234");

dataSource.setInitialSize(10);//初始化连接数

dataSource.setMaxIdle(5); //最大空闲

dataSource.setMinIdle(1); //最小空闲

 

Connection con = dataSource.getConnection();

QueryRunner qr = new QueryRunner(dataSource);

String Sql = "select * from users";

List<users> list = qr.query(Sql,new BeanListHandler<users>(users.class));

for(users u : list){

System.out.println(u.uname);

}