常用開源數據庫連接池與編寫自己的JDBC框架

常用開源數據庫連接池

數據庫連接池都要實現DataSource接口

DBCP:

連接設置

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

初始化連接

initialSize=10

最大連接數量

maxActive=50

最大空閒連接

maxIdle=20

最小空閒連接

minIdle=5

超時等待時間以毫秒爲單位 6000毫秒/1000等於60秒

maxWait=60000

JDBC驅動建立連接時附帶的連接屬性屬性的格式必須爲這樣：[屬性名=property;]

注意：”user” 與 “password” 兩個屬性會被明確地傳遞，因此這裏不需要包含他們。

connectionProperties=useUnicode=true;characterEncoding=utf8

指定由連接池所創建的連接的自動提交（auto-commit）狀態。

defaultAutoCommit=true

driver default 指定由連接池所創建的連接的只讀（read-only）狀態。

如果沒有設置該值，則“setReadOnly”方法將不被調用。（某些驅動並不支持只讀模式，如：Informix）

defaultReadOnly=

driver default 指定由連接池所創建的連接的事務級別（TransactionIsolation）。

可用值爲下列之一：（詳情可見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數據庫連接池：

配置文件：

<Context>
     <Resource name="jdbc/EmployeeDB" auth="Container"
            type="javax.sql.DataSource"
            username="root"
            password="root"
            driverClassName="com.mysql.jdbc.Driver"
            url="jdbc:mysql://localhost:3306/day16"
            initialSize="10"
            maxActive="30"
            maxIdle="4"/>
</Context>

不要忘記將數據庫驅動JAR包加入到Tomcat的lib目錄中
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();
    }

編寫自己的JDBC框架

元數據：數據庫，表，列的定義信息。
Connection.getDatabaseMetaData();

PreparedStatement.getParameterMetaData();//獲得代表PreparedStatement元數據的ParameterMetaData對象

ResultSet.getMetaData();//獲得代表ResultSet對象元數據的ResultSetMetaData對象。

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;
            }

            //創建封裝結果集的bean
            Object bean = clazz.newInstance();

            //得到結果集的元數據，以獲取結果集的信息
            ResultSetMetaData meta = rs.getMetaData();
            int count = meta.getColumnCount();
            for(int i=0;i<count;i++){
                String name = meta.getColumnName(i+1);   //獲取到結果集每列的列名  id
                Object value = rs.getObject(name);     //1

                //反射出bean上與列名相應的屬性
                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;

    }



}