將c3p0封裝為一個(gè)JDBCUtils類茬斧。管理數(shù)據(jù)庫的連接和使用。

public class JDBCTools {
    
    //處理數(shù)據(jù)庫事務(wù)的
    //提交事務(wù)
    public static void commit(Connection connection){
        if(connection != null){
            try {
                connection.commit();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    
    //回滾事務(wù)
    public static void rollback(Connection connection){
        if(connection != null){
            try {
                connection.rollback();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    
    //開始事務(wù)
    public static void beginTx(Connection connection){
        if(connection != null){
            try {
                connection.setAutoCommit(false);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    
    private static DataSource dataSource = null;

    //數(shù)據(jù)庫連接池應(yīng)只被初始化一次. 
    static{
        dataSource = new ComboPooledDataSource("c3p0");
    }
    
    public static Connection getConnection() throws Exception {
        return dataSource.getConnection();
    }

    public static void releaseDB(ResultSet resultSet, Statement statement,
            Connection connection) {

        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (statement != null) {
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (connection != null) {
            try {
                //數(shù)據(jù)庫連接池的 Connection 對(duì)象進(jìn)行 close 時(shí)
                //并不是真的進(jìn)行關(guān)閉, 而是把該數(shù)據(jù)庫連接會(huì)歸還到數(shù)據(jù)庫連接池中. 
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

}

c3p0-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>

    <named-config name="helloc3p0">
        
        <!-- 指定連接數(shù)據(jù)源的基本屬性 -->
        <property name="user">root</property>
        <property name="password">1230</property>
        <property name="driverClass">com.mysql.jdbc.Driver</property>
        <property name="jdbcUrl">jdbc:mysql:///atguigu</property>
        
        <!-- 若數(shù)據(jù)庫中連接數(shù)不足時(shí), 一次向數(shù)據(jù)庫服務(wù)器申請(qǐng)多少個(gè)連接 -->
        <property name="acquireIncrement">5</property>
        <!-- 初始化數(shù)據(jù)庫連接池時(shí)連接的數(shù)量 -->
        <property name="initialPoolSize">5</property>
        <!-- 數(shù)據(jù)庫連接池中的最小的數(shù)據(jù)庫連接數(shù) -->
        <property name="minPoolSize">5</property>
        <!-- 數(shù)據(jù)庫連接池中的最大的數(shù)據(jù)庫連接數(shù) -->
        <property name="maxPoolSize">10</property>

        <!-- C3P0 數(shù)據(jù)庫連接池可以維護(hù)的 Statement 的個(gè)數(shù) -->
        <property name="maxStatements">20</property>
        <!-- 每個(gè)連接同時(shí)可以使用的 Statement 對(duì)象的個(gè)數(shù) -->
        <property name="maxStatementsPerConnection">5</property>
    
    </named-config>
        
</c3p0-config>