JDBC+C3P0+DBCP 基本使用

1.概述

这篇文章主要说了JDBC的基本使用,包括Statement,PreparedStatement,JDBC的连接,Mysql创建用户创建数据表,C3P0的连接与配置,DBCP的连接与配置.

2.mysql的处理

这里的JDBC使用Mysql作为DBMS,请先安装Mysql,未安装的请点击这里下载,安装教程在这里,作者使用的Mysql的8.0.17版本.

(1)新建用户

随便新建一个用户,比如这里作者新建的是aa,密码是aa123bb.

create user 'aa'@'localhost' identified by 'aa123bb'

(2)建立数据表

建立测试用的数据表与数据库.

create database db;use db;create table db(    id int PRIMARY key,    name char(20));

(3)用户权限

对刚才新建的用户授权:

grant select,update,delete,insert on db.* to 'aa'@'localhost';

2.JDBC

(1)jar包

8.0.17版本在这里

各个版本的在这里下载

(2)连接

首先注册驱动,驱动需要一个url,用户名和密码,用户名和密码是上一步创建好的,url包含ip地址,端口和数据库的名字.

private static final boolean mysqlVersionGreaterThen8 = true;private static final String driver = "com.mysql" + (mysqlVersionGreaterThen8 ? ".cj" : "") + ".jdbc.Driver";private static final String ip = "127.0.0.1";private static final String port = "3306";private static String databaseName = "db";private static String url;private static String username = "aa";private static String password = "k041400r";private static Connection connection = null;public static Connection getConnection() {    try {        url = "jdbc:mysql://" + ip + ":" + port + "/" + databaseName;        Class.forName(driver);        return connection = DriverManager.getConnection(url, username, password);    } catch (Exception e) {        e.printStackTrace();    }    return null;}

这里要注意以下旧版本的mysql的驱动叫com.mysql.jdbc.Driver,新版本的叫com.mysql.cj.jdbc.Driver.还有就是url的格式:

jdbc:mysql://ip:port/database

(3)Statement

获取数据库连接后,使用createStatement方法创建Statement

• 对于select,使用Statement的executeQuery(sql),返回ResultSet
• 对于update,delete,insert,使用Statement的executeUpdate(sql)

其中sql是要执行的sql语句,一个String.

public void useStatement() {    try {        useStatementInsert();        useStatementSelect();        useStatementUpdate();        useStatementSelect();        useStatementDelete();    } catch (SQLException e) {        e.printStackTrace();    }}public void useStatementInsert() throws SQLException {    String sql = "insert into db(id,name) values(1,'23')";    Statement statement = connection.createStatement();    statement.executeUpdate(sql);}public void useStatementDelete() throws SQLException {    String sql = "delete from db";    Statement statement = connection.createStatement();    statement.executeUpdate(sql);}public void useStatementSelect() throws SQLException {    String sql = "select * from db";    Statement statement = connection.createStatement();    ResultSet resultSet = statement.executeQuery(sql);    ResultSetMetaData resultSetMetaData = resultSet.getMetaData();    int count = resultSetMetaData.getColumnCount();    while (resultSet.next()) {        for (int i = 1; i <= count; ++i) {            System.out.println(resultSet.getObject(i));        }    }}public void useStatementUpdate() throws SQLException {    Statement statement = connection.createStatement();    String sql = "update db set id = 3,name = '555' where id = 1";    statement.executeUpdate(sql);}

这里对ResultSet使用的getMetaData,可以获取结果集的各种类型信息,包括字段的类型,个数,等等.

(4)PreparedStatement

PreparedStatement与Statement使用基本一样.调用的时候先使用Connection的prepareStatement(sql)创建,然后

• 对于select,使用executeQuery(),返回一个ResultSet
• 对于update,delete,insert使用executeUpdate().

public void usePrepareStatement() {    try {        usePrepareStatementInsert();        usePrepareStatementSelect();        usePrepareStatementUpdate();        usePrepareStatementSelect();        usePrepareStatementDelete();    } catch (SQLException e) {        e.printStackTrace();    }}public void usePrepareStatementInsert() throws SQLException {    String sql = "insert into db(id,name) values(1,'23')";    PreparedStatement preparedStatement = connection.prepareStatement(sql);    preparedStatement.executeUpdate();}public void usePrepareStatementDelete() throws SQLException {    String sql = "delete from db";    PreparedStatement preparedStatement = connection.prepareStatement(sql);    preparedStatement.executeUpdate();}public void usePrepareStatementSelect() throws SQLException {    String sql = "select * from db";    PreparedStatement preparedStatement = connection.prepareStatement(sql);    ResultSet resultSet = preparedStatement.executeQuery();    ResultSetMetaData resultSetMetaData = resultSet.getMetaData();    int count = resultSetMetaData.getColumnCount();    while (resultSet.next()) {        for (int i = 1; i <= count; ++i)            System.out.println(resultSet.getObject(i));    }}public void usePrepareStatementUpdate() throws SQLException {    String sql = "update db set id = 3,name = '555' where id = 1";    PreparedStatement preparedStatement = connection.prepareStatement(sql);    preparedStatement.executeUpdate();}

(5)事务

Connection有一个setAutoCommit()方法,把它设置成false即可关闭自动提交,所有语句准备好后,一次性使用commit()提交即可.
实现回滚可以配合SavePoint使用.

3.C3P0

(1)jar包

两个:

• c3p0

• mchange-commons

(2)配置文件

src下创建一个叫c3p0.properties的文件:

c3p0.driverClass=com.mysql.cj.jdbc.Driverc3p0.jdbcUrl=jdbc:mysql://127.0.0.1:3306/dbc3p0.user=aac3p0.password=aa123bb

这里按自己需要更改即可.

(3)工具类

import com.mchange.v2.c3p0.ComboPooledDataSource;import java.sql.Connection;public class DbUtil{    private static ComboPooledDataSource C3P0dataSource = new ComboPooledDataSource("c3p0.properties");    public static void releaseConnection(Connection connection)    {        try        {            if(connection != null)                connection.close();        }        catch (Exception e)        {            e.printStackTrace();        }    }    public static Connection getC3P0Connection()    {        try        {            return C3P0dataSource.getConnection();        }        catch (Exception e)        {            e.printStackTrace();        }        return null;    }}

4.DBCP

(1)jar包

三个:

• commons-dbcp

• commons-logging

• commons-pool

(2)配置文件

src下新建dbcp.properties:

driver=com.mysql.cj.jdbc.Driverurl=jdbc:mysql://127.0.0.1:3306/dbusername=aapassword=k041400rinitialSize=10maxActive=50maxIdle=15minIdle=10maxWait=60000connectionProperties=useUnicode=true;characterEncoding=utf8defaultAutoCommit=true

分别是驱动,url,用户名,密码,初始化连接数,最大连接数,最大空闲连接数,最小空闲连接数,最大等待实际,连接属性(这里设置了编码),自动提交.

(3)工具类

import org.apache.commons.dbcp2.BasicDataSourceFactory;import java.io.InputStream;import java.sql.Connection;import java.util.Properties;import javax.sql.DataSource;public class DbUtil {    private static DataSource DBCPdataSource;    static {        try {            InputStream inputStream = DbUtil.class.getClassLoader().getResourceAsStream("dbcp.properties");            Properties properties = new Properties();            properties.load(inputStream);            DBCPdataSource = BasicDataSourceFactory.createDataSource(properties);        } catch (Exception e) {            e.printStackTrace();        }    }    public static Connection getDBCPConnection() {        try {            return DBCPdataSource.getConnection();        } catch (Exception e) {            e.printStackTrace();        }        return null;    }    public static void releaseConnection(Connection connection) {        try {            if (connection != null)                connection.close();        } catch (Exception e) {            e.printStackTrace();        }    }}

首先加载属性文件,再使用Properties的load方法将其加载到一个Properties对象中,最后交给BasicDataSourceFactory处理.

5.源码

包含了jar包,配置文件,sql文件与测试代码.

• github
• 码云