常用开源数据库连接池与编写自己的JDBC框架

2024-07-21 02:52:34

字体：大中小

来源：转载

供稿：网友

常用开源数据库连接池

数据库连接池都要实现DataSource接口

DBCP:

连接设置

driverClassName=com.MySQL.jdbc.Driver url=jdbc:mysql://localhost:3306/jdbc username=root passWord=

初始化连接

initialSize=10

最大连接数量

maxActive=50

最大空闲连接

maxIdle=20

最小空闲连接

minIdle=5

超时等待时间以毫秒为单位 6000毫秒/1000等于60秒

maxWait=60000

JDBC驱动建立连接时附带的连接属性属性的格式必须为这样：[属性名=PRoperty;]

注意：”user” 与 “password” 两个属性会被明确地传递，因此这里不需要包含他们。

connectionProperties=useUnicode=true;characterEncoding=utf8

指定由连接池所创建的连接的自动提交（auto-commit）状态。

defaultAutoCommit=true

driver default 指定由连接池所创建的连接的只读（read-only）状态。

如果没有设置该值，则“setReadOnly”方法将不被调用。（某些驱动并不支持只读模式，如：Informix）

defaultReadOnly=

driver default 指定由连接池所创建的连接的事务级别（TransactionIsolation）。

可用值为下列之一：（详情可见javadoc。）NONE,READ_UNCOMMITTED, READ_COMMITTED, REPEATABLE_READ, SERIALIZABLE

defaultTransactionIsolation=READ_COMMITTED

private static DataSource ds=null; static{ try{ InputStream in=JdbcUtils_DBCP.class.getClassLoader().getResourceAsStream("dbcpconfig.properties"); Properties prop=new Properties(); prop.load(in); BasicDataSourceFactory factory=new BasicDataSourceFactory(); ds=factory.createDataSource(prop); }catch(Exception e){ throw new ExceptionInInitializerError(e); } } public static Connection getConnection() throws SQLException{ return ds.getConnection(); }

C3P0:

配置文件：

c3p0-config.xml:

<?xml version="1.0" encoding="UTF-8"?><c3p0-config> <default-config> <property name="driverClass">com.mysql.jdbc.Driver</property> <property name="jdbcUrl">jdbc:mysql://localhost:3306/day16</property> <property name="user">root</property> <property name="password">root</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="yjw"> <property name="driverClass">com.mysql.jdbc.Driver</property> <property name="jdbcUrl">jdbc:mysql://localhost:3306/day16</property> <property name="user">root</property> <property name="password">root</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>

使用方法：

private static ComboPooledDataSource ds = null; static{ try{ ds = new ComboPooledDataSource(); }catch (Exception e) { throw new ExceptionInInitializerError(e); } } public static Connection getConnection() throws SQLException{ return ds.getConnection(); }

Jndi容器

Tomcat数据库连接池：

配置文件：

不要忘记将数据库驱动JAR包加入到Tomcat的lib目录中使用方法：

private static DataSource ds; static { try { Context initCtx = new InitialContext(); Context envCtx = (Context) initCtx.lookup("java:comp/env"); ds = (DataSource) envCtx.lookup("jdbc/EmployeeDB"); } catch (Exception e) { throw new RuntimeException(e); } } public static Connection getConnection() throws SQLException{ return ds.getConnection(); }

编写自己的JDBC框架

元数据：数据库，表，列的定义信息。 Connection.getDatabaseMetaData();

PreparedStatement.getParameterMetaData();//获得代表PreparedStatement元数据的ParameterMetaData对象

ResultSet.getMetaData();//获得代表ResultSet对象元数据的ResultSetMetaData对象。

public class JdbcUtils { private static DataSource ds = null; static{ try{ InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("dbcpconfig.properties"); Properties prop = new Properties(); prop.load(in); BasicDataSourceFactory factory = new BasicDataSourceFactory(); ds = factory.createDataSource(prop); }catch (Exception e) { throw new ExceptionInInitializerError(e); } } public static Connection getConnection() throws SQLException{ return ds.getConnection(); } public static void release(Connection conn,Statement st,ResultSet rs){ if(rs!=null){ try{ rs.close(); //throw new }catch (Exception e) { e.printStackTrace(); } rs = null; } if(st!=null){ try{ st.close(); }catch (Exception e) { e.printStackTrace(); } st = null; } if(conn!=null){ try{ conn.close(); }catch (Exception e) { e.printStackTrace(); } } } //String sql = "insert into account(id,name,money) values(?,?,?)" object[]{1,"aaa","10000"}; public static void update(String sql,Object params[]) throws SQLException{ Connection conn = null; PreparedStatement st = null; ResultSet rs = null; try{ conn = getConnection(); st = conn.prepareStatement(sql); for(int i=0;i<params.length;i++){ st.setObject(i+1,params[i]); } st.executeUpdate(); }finally{ release(conn, st, rs); } } // public static Object query(String sql,Object params[],ResultSetHandler handler) throws SQLException{ Connection conn = null; PreparedStatement st = null; ResultSet rs = null; try{ conn = getConnection(); st = conn.prepareStatement(sql); for(int i=0;i<params.length;i++){ st.setObject(i+1,params[i]); } rs = st.executeQuery(); return handler.handler(rs); }finally{ release(conn, st, rs); } }} interface ResultSetHandler{ public Object handler(ResultSet rs);}class BeanHandler implements ResultSetHandler{ private Class clazz; public BeanHandler(Class clazz){ this.clazz = clazz; } public Object handler(ResultSet rs) { try{ if(!rs.next()){ return null; } //创建封装结果集的bean Object bean = clazz.newInstance(); //得到结果集的元数据，以获取结果集的信息 ResultSetMetaData meta = rs.getMetaData(); int count = meta.getColumnCount(); for(int i=0;i<count;i++){ String name = meta.getColumnName(i+1); //获取到结果集每列的列名 id Object value = rs.getObject(name); //1 //反射出bean上与列名相应的属性 Field f = bean.getClass().getDeclaredField(name); f.setaccessible(true); f.set(bean, value); } return bean; }catch (Exception e) { throw new RuntimeException(e); } }}class BeanListHandler implements ResultSetHandler{ private Class clazz; public BeanListHandler(Class clazz){ this.clazz = clazz; } public Object handler(ResultSet rs) { List list = new ArrayList(); try{ while(rs.next()){ Object bean = clazz.newInstance(); ResultSetMetaData meta = rs.getMetaData(); int count = meta.getColumnCount(); for(int i=0;i<count;i++){ String name = meta.getColumnName(i+1); Object value = rs.getObject(name); Field f = bean.getClass().getDeclaredField(name); f.setAccessible(true); f.set(bean, value); } list.add(bean); } }catch (Exception e) { throw new RuntimeException(e); } return list; }}

上一篇：Redis学习笔记

下一篇：ORA-28000: the account is locked-的解决办法