Java从数据库中读取Blob对象图片并显示的方法
本文实例讲述了Java从数据库中读取Blob对象图片并显示的方法。分享给大家供大家参考。具体实现方法如下：
第一种方法：
大致方法就是，从数据库中读出Blob的流来，写到页面中去：
Connectionconn=DBManager.getConnection();
Stringsql="SELECTpictureFROMteacherWHEREid=1";
PreparedStatementps=null;
ResultSetrs=null;
InputStreamis=null;
OutputStreamos=null;
try{
ps=conn.prepareStatement(sql);
rs=ps.executeQuery();
if(rs.next()){
is=rs.getBinaryStream(1);
}
response.setContentType("text/html");
os=response.getOutputStream();
intnum;
bytebuf[]=newbyte[1024];
while( (num=is.read(buf))!=-1 ){
os.write(buf,0,num);
}
}catch(SQLExceptione){
e.printStackTrace();
}
try{
is.close();
os.close();
rs.close();
ps.close();
}catch(SQLExceptione){
e.printStackTrace();
}在页面中：
<% Stringpath=request.getContextPath(); StringbasePath=request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <imgname="pic"src="<%=basePath+"servlet/DownloadAsStream"%>"/>
搞定。
第二种方法：
整个流程分为四步，连接oracle数据库->读取blob图片字段->对图片进行缩放->把图片展示在jsp页面上。
importjava.sql.*;
importjava.io.*;
importjavax.imageio.ImageIO;
importjava.awt.image.BufferedImage;
importjava.awt.image.AffineTransformOp;
importjava.awt.geom.AffineTransform;
publicclassOracleQueryBean{
privatefinalStringoracleDriverName="oracle.jdbc.driver.OracleDriver";
privateConnectionmyConnection=null;
privateStringstrTabName;
privateStringstrIDName;
privateStringstrImgName;
publicOracleQueryBean(){
try{
Class.forName(oracleDriverName);
}catch(ClassNotFoundExceptionex){
System.out.println("加载jdbc驱动失败,原因:"+ex.getMessage());
}
}
publicConnectiongetConnection(){
try{
//用户名+密码;以下使用的Test就是Oracle里的表空间
//从配置文件中读取数据库信息
GetParaoGetPara=newGetPara();
StringstrIP=oGetPara.getPara("serverip");
StringstrPort=oGetPara.getPara("port");
StringstrDBName=oGetPara.getPara("dbname");
StringstrUser=oGetPara.getPara("user");
StringstrPassword=oGetPara.getPara("password");
this.strTabName=oGetPara.getPara("tablename");
this.strIDName=oGetPara.getPara("imgidname");
this.strImgName=oGetPara.getPara("imgname");
StringoracleUrlToConnect="jdbc:oracle:thin:@"+strIP+":"+strPort+":"+strDBName;
this.myConnection=DriverManager.getConnection(oracleUrlToConnect,strUser,strPassword);
}catch(Exceptionex){
System.out.println("Cannotgetconnection:"+ex.getMessage());
System.out.println("请检测配置文件中的数据库信息是否正确.");
}
returnthis.myConnection;
}
}
2.读取blob字段
在OracleQueryBean类中增加一个函数，来进行读取，具体代码如下：
publicbyte[]GetImgByteById(StringstrID,intw,inth){
//System.out.println("Getimgdatawhichidis"+nID);
if(myConnection==null)
this.getConnection();
byte[]data=null;
try{
Statementstmt=myConnection.createStatement();
ResultSetmyResultSet=stmt.executeQuery("select"+this.strIDName+"from"+this.strTabName+"where"+this.strIDName+"="+strID);
StringBuffermyStringBuffer=newStringBuffer();
if(myResultSet.next()){
java.sql.Blobblob=myResultSet.getBlob(this.strImgName);
InputStreaminStream=blob.getBinaryStream();
try{
longnLen=blob.length();
intnSize=(int)nLen;
//System.out.println("imgdatasizeis:"+nSize);
data=newbyte[nSize];
inStream.read(data);
inStream.close();
}catch(IOExceptione){
System.out.println("获取图片数据失败,原因:"+e.getMessage());
}
data=ChangeImgSize(data,w,h);
}
System.out.println(myStringBuffer.toString());
myConnection.commit();
myConnection.close();
}catch(SQLExceptionex){
System.out.println(ex.getMessage());
}
returndata;
}
3.缩放图片
因为图片的大小可能不一致，但是在页面中输出的大小需要统一，所以需要
在OracleQueryBean类中增加一个函数，来进行缩放，具体代码如下：
privatebyte[]ChangeImgSize(byte[]data,intnw,intnh){
byte[]newdata=null;
try{
BufferedImagebis=ImageIO.read(newByteArrayInputStream(data));
intw=bis.getWidth();
inth=bis.getHeight();
doublesx=(double)nw/w;
doublesy=(double)nh/h;
AffineTransformtransform=newAffineTransform();
transform.setToScale(sx,sy);
AffineTransformOpato=newAffineTransformOp(transform,null);
//原始颜色
BufferedImagebid=newBufferedImage(nw,nh,BufferedImage.TYPE_3BYTE_BGR);
ato.filter(bis,bid);
//转换成byte字节
ByteArrayOutputStreambaos=newByteArrayOutputStream();
ImageIO.write(bid,"jpeg",baos);
newdata=baos.toByteArray();
}catch(IOExceptione){
e.printStackTrace();
}
returnnewdata;
}
4.展示在页面
页面使用OracleQueryBean来根据用户提供的图片id进行查询，在读取并进行缩放后，通过jsp页面进行展示，具体代码如下：
<%@pagelanguage="java"contentType="text/html;;charset=gbk"%>
<jsp:useBeanid="OrcleQuery"scope="page"class="HLFtiDemo.OracleQueryBean"/>
<%
response.setContentType("image/jpeg");
//图片在数据库中的ID
StringstrID=request.getParameter("id");
//要缩略或放大图片的宽度
StringstrWidth=request.getParameter("w");
//要缩略或放大图片的高度
StringstrHeight=request.getParameter("h");
byte[]data=null;
if(strID!=null){
intnWith=Integer.parseInt(strWidth);
intnHeight=Integer.parseInt(strHeight);
//获取图片的byte数据
data=OrcleQuery.GetImgByteById(strID,nWith,nHeight);
ServletOutputStreamop=response.getOutputStream();
op.write(data,0,data.length);
op.close();
op=null;
response.flushBuffer();
//清除输出流，防止释放时被捕获异常
out.clear();
out=pageContext.pushBody();
}
%>
5.OracleQueryBean查询类的整体代码
OracleQueryBean.java文件代码如下所示：
importjava.sql.*;
importjava.io.*;
importjavax.imageio.ImageIO;
importjava.awt.image.BufferedImage;
importjava.awt.image.AffineTransformOp;
importjava.awt.geom.AffineTransform;
publicclassOracleQueryBean{
privatefinalStringoracleDriverName="oracle.jdbc.driver.OracleDriver";
privateConnectionmyConnection=null;
privateStringstrTabName;
privateStringstrIDName;
privateStringstrImgName;
publicOracleQueryBean(){
try{
Class.forName(oracleDriverName);
}catch(ClassNotFoundExceptionex){
System.out.println("加载jdbc驱动失败,原因:"+ex.getMessage());
}
}
publicConnectiongetConnection(){
try{
//用户名+密码;以下使用的Test就是Oracle里的表空间
//从配置文件中读取数据库信息
GetParaoGetPara=newGetPara();
StringstrIP=oGetPara.getPara("serverip");
StringstrPort=oGetPara.getPara("port");
StringstrDBName=oGetPara.getPara("dbname");
StringstrUser=oGetPara.getPara("user");
StringstrPassword=oGetPara.getPara("password");
this.strTabName=oGetPara.getPara("tablename");
this.strIDName=oGetPara.getPara("imgidname");
this.strImgName=oGetPara.getPara("imgname");
StringoracleUrlToConnect="jdbc:oracle:thin:@"+strIP+":"+strPort+":"+strDBName;
this.myConnection=DriverManager.getConnection(oracleUrlToConnect,strUser,strPassword);
}catch(Exceptionex){
System.out.println("Cannotgetconnection:"+ex.getMessage());
System.out.println("请检测配置文件中的数据库信息是否正确.");
}
returnthis.myConnection;
}
publicbyte[]GetImgByteById(StringstrID,intw,inth){
//System.out.println("Getimgdatawhichidis"+nID);
if(myConnection==null)
this.getConnection();
byte[]data=null;
try{
Statementstmt=myConnection.createStatement();
ResultSetmyResultSet=stmt.executeQuery("select"+this.strIDName+"from"+this.strTabName+"where"+this.strIDName+"="+strID);
StringBuffermyStringBuffer=newStringBuffer();
if(myResultSet.next()){
java.sql.Blobblob=myResultSet.getBlob(this.strImgName);
InputStreaminStream=blob.getBinaryStream();
try{
longnLen=blob.length();
intnSize=(int)nLen;
//System.out.println("imgdatasizeis:"+nSize);
data=newbyte[nSize];
inStream.read(data);
inStream.close();
}catch(IOExceptione){
System.out.println("获取图片数据失败,原因:"+e.getMessage());
}
data=ChangeImgSize(data,w,h);
}
System.out.println(myStringBuffer.toString());
myConnection.commit();
myConnection.close();
}catch(SQLExceptionex){
System.out.println(ex.getMessage());
}
returndata;
}
publicbyte[]GetImgByteById(StringstrID){ //System.out.println("Getimgdatawhichidis"+nID); if(myConnection==null) this.getConnection(); byte[]data=null; try{ Statementstmt=myConnection.createStatement(); ResultSetmyResultSet=stmt.executeQuery("select"+this.strIDName+"from"+this.strTabName+"where"+this.strIDName+"="+strID); StringBuffermyStringBuffer=newStringBuffer(); if(myResultSet.next()){ java.sql.Blobblob=myResultSet.getBlob(this.strImgName); InputStreaminStream=blob.getBinaryStream(); try{ longnLen=blob.length(); intnSize=(int)nLen; data=newbyte[nSize]; inStream.read(data); inStream.close(); }catch(IOExceptione){ System.out.println("获取图片数据失败,原因:"+e.getMessage()); } } System.out.println(myStringBuffer.toString()); myConnection.commit(); myConnection.close(); }catch(SQLExceptionex){ System.out.println(ex.getMessage()); } returndata; }
privatebyte[]ChangeImgSize(byte[]data,intnw,intnh){ byte[]newdata=null; try{ BufferedImagebis=ImageIO.read(newByteArrayInputStream(data)); intw=bis.getWidth(); inth=bis.getHeight(); doublesx=(double)nw/w; doublesy=(double)nh/h; AffineTransformtransform=newAffineTransform(); transform.setToScale(sx,sy); AffineTransformOpato=newAffineTransformOp(transform,null); //原始颜色 BufferedImagebid=newBufferedImage(nw,nh,BufferedImage.TYPE_3BYTE_BGR); ato.filter(bis,bid); //转换成byte字节 ByteArrayOutputStreambaos=newByteArrayOutputStream(); ImageIO.write(bid,"jpeg",baos); newdata=baos.toByteArray(); }catch(IOExceptione){ e.printStackTrace(); } returnnewdata; } }