JDBC+C3P0+DBCP 基本使用

1.概述

這篇文章主要說了JDBC的基本使用,包括Statement,PreparedStatement,JDBC的鏈接,Mysql建立用戶建立數據表,C3P0的鏈接與配置,DBCP的鏈接與配置.

2.mysql的處理

這裏的JDBC使用Mysql做爲DBMS,請先安裝Mysql,未安裝的請點擊這裏下載,安裝教程在這裏,做者使用的Mysql的8.0.17版本.

(1)新建用戶

隨便新建一個用戶,好比這裏做者新建的是aa,密碼是aa123bb.

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

(2)創建數據表

創建測試用的數據表與數據庫.

create database db;
use db;

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

(3)用戶權限

對剛纔新建的用戶受權:

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

2.JDBC

(1)jar包

8.0.17版本在這裏

各個版本的在這裏下載

(2)鏈接

首先註冊驅動,驅動須要一個url,用戶名和密碼,用戶名和密碼是上一步建立好的,url包含ip地址,端口和數據庫的名字.

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;
}

這裏要注意如下舊版本的mysql的驅動叫com.mysql.jdbc.Driver,新版本的叫com.mysql.cj.jdbc.Driver.還有就是url的格式:

jdbc:mysql://ip:port/database

(3)Statement

獲取數據庫鏈接後,使用createStatement方法建立Statement

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

其中sql是要執行的sql語句,一個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);
}

這裏對ResultSet使用的getMetaData,能夠獲取結果集的各類類型信息,包括字段的類型,個數,等等.

(4)PreparedStatement

PreparedStatement與Statement使用基本同樣.調用的時候先使用Connection的prepareStatement(sql)建立,而後

• 對於select,使用executeQuery(),返回一個ResultSet
• 對於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)事務

Connection有一個setAutoCommit()方法,把它設置成false便可關閉自動提交,全部語句準備好後,一次性使用commit()提交便可. 實現回滾能夠配合SavePoint使用.

3.C3P0

(1)jar包

兩個:

• c3p0

• mchange-commons

(2)配置文件

src下建立一個叫c3p0.properties的文件:

c3p0.driverClass=com.mysql.cj.jdbc.Driver
c3p0.jdbcUrl=jdbc:mysql://127.0.0.1:3306/db
c3p0.user=aa
c3p0.password=aa123bb

這裏按本身須要更改便可.

(3)工具類

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

三個:

• commons-dbcp

• commons-logging

• commons-pool

(2)配置文件

src下新建dbcp.properties:

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/db
username=aa
password=k041400r
initialSize=10
maxActive=50
maxIdle=15
minIdle=10
maxWait=60000
connectionProperties=useUnicode=true;characterEncoding=utf8
defaultAutoCommit=true

分別是驅動,url,用戶名,密碼,初始化鏈接數,最大鏈接數,最大空閒鏈接數,最小空閒鏈接數,最大等待實際,鏈接屬性(這裏設置了編碼),自動提交.

(3)工具類

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();
        }
    }
}

首先加載屬性文件,再使用Properties的load方法將其加載到一個Properties對象中,最後交給BasicDataSourceFactory處理.

5.源碼

包含了jar包,配置文件,sql文件與測試代碼.

• github
• 碼雲