JDBC 10 数据库连接池 C3P0_综合

2.7 数据库连接池 C3P0

c3p0-0.9.5.5 mchange-commons-java-0.2.20

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C3P0 的配置是 xml 文件，所以我们需要写一份 xml 文件的配置。

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config><default-config><property name="jdbcUrl">jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&amp;charaterEncoding=utf8&amp;useSSL=true&amp;serverTimezone=UTC</property><property name="user">root</property><property name="password">123123</property><property name="acquireIncrement">5</property><property name="initialPoolSize">10</property><property name="minPoolSize">5</property><property name="maxPoolSize">20</property></default-config><named-config name="MySQL"><property name="jdbcUrl">jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&amp;charaterEncoding=utf8&amp;useSSL=true&amp;serverTimezone=UTC</property><property name="user">root</property><property name="password">123123</property><property name="acquireIncrement">5</property><property name="initialPoolSize">10</property><property name="minPoolSize">5</property><property name="maxPoolSize">20</property></named-config>
</c3p0-config>

下面的 named-config 和上面的 default-config 表示两个配置内容，如果你想使用下面的配置内容，就必须标注为 “MySQL”，如果你只想用默认的配置内容，则可以什么都不用提供。

//什么都不写，那么就用默认的配置内容。 dataSource = new ComboPooledDataSource();

package com.muquanyu.lesson03;import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.apache.commons.dbcp2.BasicDataSource;
import org.apache.commons.dbcp2.BasicDataSourceFactory;import javax.sql.DataSource;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;public class JdbcUtils_C3P0 {
    //private static ComboPooledDataSource dataSource = null;private static DataSource dataSource = null;static {
    try {
    //代码版配置/*dataSource = new ComboPooledDataSource();dataSource.setDriverClass();dataSource.setUser();dataSource.setPassword();dataSource.setJdbcUrl();dataSource.setMaxPoolSize();dataSource.setMinPoolSize();*///创建数据源 (工厂模式）--> 创建//什么都不写，那么就用默认的配置内容。dataSource = new ComboPooledDataSource();} catch (Exception e) {
    e.printStackTrace();}}//获取连接public static Connection getConnection() throws SQLException {
    return dataSource.getConnection();}//释放资源public static void release(Connection conn, Statement st, ResultSet rs) {
    if (rs != null) {
    try {
    rs.close();} catch (SQLException e) {
    e.printStackTrace();}}if (st != null) {
    try {
    st.close();} catch (SQLException e) {
    e.printStackTrace();}}if (conn != null) {
    try {
    conn.close();} catch (SQLException e) {
    e.printStackTrace();}}}
}

package com.muquanyu.lesson03;import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;public class C3P0Demo {
    public static void main(String[] args) throws SQLException {
    Connection connection = null;Statement statement = null;ResultSet resultSet = null;try {
    connection = JdbcUtils_C3P0.getConnection(); //获取到数据库对象statement = connection.createStatement(); // 获取到 SQL 执行对象String sql = "insert into `users`(`id`,`NAME`,`PASSWORD`,`email`,`birthday`)" +" values('4','罗翔','159159','159159@23.com','1985-8-1')";int num = statement.executeUpdate(sql);if (num > 0) {
    System.out.println("插入数据成功！");}} catch (SQLException e) {
    e.printStackTrace();}String sql = "select * from `users`";resultSet = statement.executeQuery(sql);while (resultSet.next()) {
    System.out.println(resultSet.getInt("id") + "|" + resultSet.getString("NAME")+ "|" + resultSet.getObject("PASSWORD") + "|" + resultSet.getString("email")+ "|" + resultSet.getDate("birthday"));}JdbcUtils_C3P0.release(connection, statement, resultSet);}
}

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到了后期，你会发现很多开源的强大的 jar包，别人写的轮子和库都是 apache 的！

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