莊周夢(mèng)蝶

?<class name="com.denny_blue.hibernate.User"
??????? table="t_user"
??????? dynamic-update="true"
??????? dynamic-insert="true"
??????? batch-size="3">
??<id name="id"
????? column="id"
????? type="java.lang.Integer">
???<generator class="native"/>
??</id>
??<property name="name" column="name" type="java.lang.String" lazy="true"/>
??<property name="photo" column="photo" type="java.sql.Blob"/>

?</class>

</hibernate-mapping>

對(duì)應(yīng)的hibernate.cfg.xml配置文件，不再列出，請(qǐng)參照hibernate文檔自行設(shè)定．

ＯＫ，做了這一步，我們寫個(gè)測(cè)試類來(lái)進(jìn)行單元測(cè)試：

package com.denny_blue.test;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Blob;

import org.hibernate.Hibernate;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

import com.denny_blue.hibernate.User;

import junit.framework.TestCase;

public class HibernateTest extends TestCase {
??????? private Session session;
?protected void setUp() throws Exception {
??try{
???Configuration config=new Configuration().configure();
???SessionFactory sf=config.buildSessionFactory();
???session=sf.openSession();
??}catch(HibernateException e){
???e.printStackTrace();
??}
?}

?protected void tearDown() throws Exception {
??try{
???session.close();
??}catch(HibernateException e){
???e.printStackTrace();
??}
?}
?
?public void testSave()throws FileNotFoundException,IOException{
??User user=new User();
??user.setName("jordan");
??FileInputStream in=new FileInputStream("C://test.gif");
??Blob photo=Hibernate.createBlob(in);
??user.setPhoto(photo);
??Transaction tx=null;
??try{
??tx=session.beginTransaction();
??session.saveOrUpdate(user);
??tx.commit();
??}catch(HibernateException e){
???if(tx!=null)
????tx.rollback();
???e.printStackTrace();
??}finally{
???in.close();
??}
?}
?public void testLoad()throws Exception{
??try{
???User user=(User)session.load(User.class, new Integer(1));
???Blob photo=user.getPhoto();
???InputStream in=photo.getBinaryStream();
???FileOutputStream out=new FileOutputStream("C://out//test2.gif");
???byte [] buf=new byte[1024];
???int len;
???while((len=in.read(buf))!=-1){
????out.write(buf, 0, len);
???}
???in.close();
???out.close();
??}catch(HibernateException e){
???e.printStackTrace();
??}
?}

}
我們讀取C盤目錄下的test.gif并存儲(chǔ)到數(shù)據(jù)庫(kù)中，然后再取出來(lái)寫入C:/out目錄，此時(shí)你可以查看下數(shù)據(jù)表中photo顯示為blob,表示已經(jīng)成功存入．值的注意的代碼片段就是：

FileInputStream in=new FileInputStream("C://test.gif");
??Blob photo=Hibernate.createBlob(in);
我們這里是從磁盤中讀取圖片，實(shí)際應(yīng)用中你可以利用上傳組件得到圖片的２進(jìn)制數(shù)據(jù)流，并利用Hibernate.createBlob方法來(lái)構(gòu)造相應(yīng)的Blob對(duì)象．而取圖片則使用

InputStream in=photo.getBinaryStream();

這只是個(gè)簡(jiǎn)單的測(cè)試類，如果我想從數(shù)據(jù)庫(kù)中取出圖片并現(xiàn)實(shí)在頁(yè)面上該如何做呢？其實(shí)也很簡(jiǎn)單，我們先要寫一個(gè)servlet，在它的service方法中取出圖片，并＂畫＂到指定頁(yè)面上．

package com.easyjf.asp.action;

import java.io.InputStream;
import java.io.OutputStream;
import java.sql.Blob;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import com.denny)blue.hibernate.User;

public class Test extends HttpServlet {

?/**
? * Destruction of the servlet. <br>
? */
?private Session session;
?public void destroy() {
??try{
???session.close();
??}catch(HibernateException e){
???e.printStackTrace();
??}
?}

?/**
? * Initialization of the servlet. <br>
? *
? * @throws ServletException if an error occure
? */
?public void init() throws ServletException {
??try{
???Configuration config=new Configuration().configure();
???SessionFactory sf=config.buildSessionFactory();
???session=sf.openSession();
??}catch(HibernateException e){
???e.printStackTrace();
??}
?}
??? public void doGet(HttpServletRequest request,HttpServletResponse response)
??? {
??? ?try{
???User user=(User)session.load(User.class, new Integer(1));
???Blob photo=user.getPhoto();
???InputStream in=photo.getBinaryStream();
???OutputStream out=response.getOutputStream();
???byte [] buf=new byte[1024];
???int len;
???while((len=in.read(buf))!=-1){
????out.write(buf, 0, len);
???}
???in.close();
???out.close();
??}catch(Exception e){
???e.printStackTrace();
??}
??? }

}

通過(guò)response.getOutputStream取得輸出流，其他就與上段代碼一致．servlet寫好了，怎么在頁(yè)面調(diào)用呢？那就更簡(jiǎn)單啦，直接在頁(yè)面的img標(biāo)簽的src屬性上調(diào)用該servlet即可，如：

<img id="test" src="/servlet/Test"/>

?

簡(jiǎn)單的例子，希望對(duì)初學(xué)者有幫助．

附記:如果不希望在servlet(或者action之類)中進(jìn)行保存操作,希望在DAO進(jìn)行此操作,那么InputStream的關(guān)閉問(wèn)題可以通過(guò)hibernate的interceptor機(jī)制解決