我的持久层——MyPersistance

　　最近在努力地学习Hibernate，为了能更好地理解持久层的原理，仿照书上的例子做了一个松耦合的小持久层，这里仅仅是为了体现松耦合关系，其他那些Connection pool, Statement pool都没有考虑。这个小持久层，共有7个类，其中包括一个测试用的类。以下是源代码：

 

 

DBHelper.java(这个类用于数据库的操作)

 package cn.relyn.common;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;public class DBHelper {/** * connect MySQL * * @return */public static Connection getConnection() {try {Class.forName("org.gjt.mm.mysql.Driver");} catch (ClassNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}try {Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/test", "root", "");return conn;} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();return null;}}/** * connect Oracle * * @return */public static Connection getConnection2() {try {Class.forName("oracle.jdbc.driver.OracleDriver");Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:WCZY", "RELYN", "RELYN");return conn;} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();return null;}}/** * close Connection * * @param conn */public static void releaseConnection(Connection conn) {if (conn != null) {try {conn.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}conn = null;}}}

 

 

ClassToolkit.java(这个类用于动态加载某个类)

 package cn.relyn.common;public class ClassToolKit {public static Class loadClass(String className) {Class cls = null;try {cls = Thread.currentThread().getContextClassLoader().loadClass(className);} catch (ClassNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}if (cls == null) {try {cls = Class.forName(className);} catch (ClassNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}}return cls;}} 

 

 

DAOFactory.java(这个类是所有DAO类的工厂)

 package cn.relyn.common;import java.util.HashMap;import cn.relyn.dao.impl.RelynDAO_MySQL;public class DAOFactory {private static HashMap<Class<?>, Class<?>> daoMap = null;public static Object getDAO(Class daoInterface) {daoMap = new HashMap<Class<?>, Class<?>>();//这里的两个全限定名应该是从配置文件里面读取的，这里为了方便就不使用配置文件了daoMap.put(ClassToolKit.loadClass("cn.relyn.dao.iface.RelynDAO"),ClassToolKit.loadClass("cn.relyn.dao.impl.RelynDAO_MySQL"));Object dao = null;try {dao = daoMap.get(daoInterface).newInstance();} catch (InstantiationException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IllegalAccessException e) {// TODO Auto-generated catch blocke.printStackTrace();}return dao;}} 

 

 

RelynDAO.java(这是一个DAO接口)

 package cn.relyn.dao.iface;import java.util.List;import cn.relyn.entity.Relyn;public interface RelynDAO {public abstract void save(Relyn relyn);public abstract List findAll();}

 

 

RelynDAO_MySQL.java(这是RelynDAO的MySQL实现)

package cn.relyn.dao.impl;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.util.ArrayList;import java.util.List;import cn.relyn.common.DBHelper;import cn.relyn.dao.iface.RelynDAO;import cn.relyn.entity.Relyn;public class RelynDAO_MySQL implements RelynDAO {/* (non-Javadoc) * @see cn.relyn.dao.RelynDAO#save(cn.relyn.entity.Relyn) */public void save(Relyn relyn) {Connection conn = null;PreparedStatement pstmt = null;conn = DBHelper.getConnection();try {pstmt = conn.prepareStatement("UPDATE relyn SET relyn_name = ? WHERE relyn_id = ?");pstmt.setString(1, relyn.getRelynName());pstmt.setInt(2, relyn.getRelynId());pstmt.executeUpdate();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();} finally {if (conn != null) {if (pstmt != null) {try {pstmt.close();} catch (SQLException e) {e.printStackTrace();}}try {conn.close();} catch (SQLException e) {e.printStackTrace();}}}}public List findAll() {// TODO Auto-generated method stubConnection conn = null;ResultSet rs = null;PreparedStatement pstmt = null;Relyn relyn;List list = new ArrayList();conn = DBHelper.getConnection();try {pstmt = conn.prepareStatement("SELECT * FROM relyn");rs = pstmt.executeQuery();while (rs.next()) {relyn = new Relyn();relyn.setRelynId(rs.getInt(1));relyn.setRelynName(rs.getString(2));list.add(relyn);}return list;} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();} finally {if (conn != null) {if (pstmt != null) {try {pstmt.close();} catch (SQLException e) {e.printStackTrace();}}try {conn.close();} catch (SQLException e) {e.printStackTrace();}}}return null;}}

 

 

Relyn.java(这是一个实体类)

package cn.relyn.entity;public class Relyn {private Integer relynId;private String relynName;public Integer getRelynId() {return relynId;}public void setRelynId(Integer relynId) {this.relynId = relynId;}public String getRelynName() {return relynName;}public void setRelynName(String relynName) {this.relynName = relynName;}}

 

 

Test.java(包含main方法的测试类)

package cn.relyn.test;import java.util.List;import cn.relyn.common.DAOFactory;import cn.relyn.dao.iface.RelynDAO;import cn.relyn.dao.impl.RelynDAO_MySQL;import cn.relyn.entity.Relyn;public class Test {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubRelynDAO relynDAO = (RelynDAO) DAOFactory.getDAO(RelynDAO.class);Relyn relyn = new Relyn();relyn.setRelynName("you");relyn.setRelynId(1);relynDAO.save(relyn);List<Relyn> list = relynDAO.findAll();for (Relyn r : list) {System.out.println("id-->" + r.getRelynId());System.out.println("name-->" + r.getRelynName());}}}

 

 

这个持久层的主要思想就是通过DAO接口，在DAO工厂工厂类的协同下取得DAO的实现类，然后调用其方法，做到完全解耦^_^