数据库连接池

jar：commons-pool.jar、commons-dbcp.jar

BasicDataSource ds = new BasicDataSource();
ds.setUsername("root");
ds.setPassword("123");
ds.setUrl("jdbc:mysql://localhost:3306/mydb1");
ds.setDriverClassName("com.mysql.jdbc.Driver");
   
ds.setMaxActive(20); //最大连接数
ds.setMaxIdle(10); //最大空闲
ds.setInitialSize(10) ;//初始化
ds.setMinIdle(2) ;//最小空闲
ds.setMaxWait(1000) ;//最大等待时间
  
Connection con = ds.getConnection();

jar：c3p0-0.9.2-pre1.jar、c3p0-oracle-thin-extras-0.9.2-pre1.jar、mchange-commons-0.2.jar
ComboPooledDataSource ds = new ComboPooledDataSource();
ds.setJdbcUrl("jdbc:mysql://localhost:3306/mydb1");
ds.setUser("root");
ds.setPassword("123");
ds.setDriverClass("com.mysql.jdbc.Driver");
   
ds.setAcquireIncrement(5) ;/*每次增加五*/
ds.setInitialPoolSize(20) ;//初始化连接数
ds.setMinPoolSize(2) ;//最少连接
ds.setMaxPoolSize(50) ;//最多连接
  
Connection con = ds.getConnection();

<default-config>
  <property name="xxx">XXX</property>
</defualt-config>

<named-config name="orcale-config">
  <property name="xxx">XXX</property>
</named-config>

    /**
     * 配置文件的默认配置
     * @throws SQLException 
     */
    @Test
    public void fun2() throws SQLException{
        /**
         * 在创建连接池对象时，这个对象就会自动加载配置文件！不用我们来指定
         */
        ComboPooledDataSource dataSource  = new ComboPooledDataSource();
        
        Connection con = dataSource.getConnection();
        System.out.println(con);
        con.close();
    }
    
    /**
     * 使用命名配置信息
     * @throws SQLException
     */
    @Test
    public void fun3() throws SQLException{
        /**
         * 构造器的参数指定命名配置元素的名称！
         * <named-config name="oracle-config"> 
         */
        ComboPooledDataSource dataSource  = new ComboPooledDataSource("oracle-config");
        
        Connection con = dataSource.getConnection();
        System.out.println(con);
        con.close();
    }
}

<Context>  
  <Resource name="myc3p0" 
   type="com.mchange.v2.c3p0.ComboPooledDataSource"
   factory="org.apache.naming.factory.BeanFactory"
   user="root" 
   password="123" 
   classDriver="com.mysql.jdbc.Driver"    
   jdbcUrl="jdbc:mysql://127.0.0.1/mydb1"
   maxPoolSize="20"
   minPoolSize ="5"
   initialPoolSize="10"
   acquireIncrement="2"/>
</Context>  

public class JdbcUtils {
 private static DataSource dataSource = new ComboPooledDataSource();
 public static DataSource getDataSource() {
  return dataSource;
 }
 public static Connection getConnection() {
  try {
   return dataSource.getConnection();
  } catch (Exception e) {
   throw new RuntimeException(e);
  }
 }
}

public void fun1() throws SQLException {
 QueryRunner qr = new QueryRunner();
 String sql = "insert into user values(?,?,?)";
 qr.update(JdbcUtils.getConnection(), sql, "u1", "zhangSan", "123");
}

DataSource ds = JdbcUtils.getDataSource();
QueryRunner qr = new QueryRunner(ds);
String sql = "select * from tab_student";

// 把结果集转换成Bean
Student stu = qr.query(sql, new BeanHandler<Student>(Student.class));

// 把结果集转换成Bean的List
List<Student> list = qr.query(sql, new BeanListHandler<Student>(Student.class));

// 把结果集转换成Map
Map<String,Object> map = qr.query(sql, new MapHandler());

// 把结果集转换成List<Map>
List<Map<String,Object>> list = qr.query(sql, new MapListHandler() );

// 把结果集转换成一列的List
List<Object> list = qr.query(sql, new ColumnListHandler("name")) ;

// 把结果转换成单行单列的值
Number number = (Number)qr.query(sql, new ScalarHandler());

 DataSource ds = JdbcUtils.getDataSource();
 QueryRunner qr = new QueryRunner(ds);
 String sql = "insert into tab_student values(?,?,?,?)";
 Object[][] params = new Object[10][]; //表示 要插入10行记录
 for(int i = 0; i < params.length; i++) {
  params[i] = new Object[]{"S_300" + i, "name" + i, 30 + i, i%2==0?"男":"女"};
 }
 qr.batch (sql, params);