JAVA读取Oracle中的blob图片字段并显示

近期，在给客户做一个Demo页面时，需要用JAVA读取Oracle中的blob图片字段并显示，在此过程中，遇到一些问题，例如：连接Oracle数据库读取blob字段数据，对图片byte数据进行缩放等；特此记录，给自己备忘，给大家参考。

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。

下面进行详细描述：

1.java连接Oracle

注：数据库是Oracle10g版本为10.2.0,在数据库中，图片字段类型为BLOB。

java中通常使用的是通过jdbc驱动来连接数据库，oracle也不例外，因此必须下载一个Oracle驱动的jdbc需要去网上进行下载,名称为ojdbc14.jar。

下载地址为:

下载了驱动之后，可以使用驱动里提供的接口进行连接，具体代码如下：

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;

/*图片表名*/

privateStringstrTabName;

/*图片ID字段名*/

privateStringstrIDName;

/*图片字段名*/

privateStringstrImgName;

/**

*加载java连接Oracle的jdbc驱动

*/

publicOracleQueryBean(){

try{

Class.forName(oracleDriverName);

}catch(ClassNotFoundException ex){

System.out.println("加载jdbc驱动失败,原因:"+ ex.getMessage());

}

}

/**

*获取Oracle连接对象

*@returnConnection

*/

publicConnection getConnection(){

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

GetPara

oGetPara =newGetPara();

String

strIP = oGetPara.getPara("serverip");

String

strPort = oGetPara.getPara("port");

String

strDBName = oGetPara.getPara("dbname");

String

strUser = oGetPara.getPara("user");

String

strPassword = oGetPara.getPara("password");

this.strTabName=

oGetPara.getPara("tablename");

this.strIDName=

oGetPara.getPara("imgidname");

this.strImgName=

oGetPara.getPara("imgname");

String

oracleUrlToConnect ="jdbc:oracle:thin:@"+strIP+":"+strPort+":"+strDBName;

this.myConnection= DriverManager.getConnection(oracleUrlToConnect,

strUser, strPassword);

}catch(Exception ex){

System.out.println("Can not get connection:"+ 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：

/**

*根据图片在数据库中的ID进行读取

*@paramstrID图片字段ID

*@paramw需要缩到的宽度

*@paramh需要缩到高度

*@return

*/

publicbyte[]

GetImgByteById(String strID,intw,inth){

//System.out.println("Get img data which id is

" + nID);

if(myConnection==null)

this.getConnection();

byte[] data =null;

try{

Statement stmt =myConnection.createStatement();

ResultSet myResultSet = stmt.executeQuery("select "+this.strIDName+" from "+this.strTabName+" where "+this.strIDName+"="+ strID);

StringBuffer myStringBuffer =newStringBuffer();

if(myResultSet.next()) {

java.sql.Blob blob = myResultSet.getBlob(this.strImgName);

InputStream inStream = blob.getBinaryStream();

try{

longnLen = blob.length();

intnSize = (int) nLen;

//System.out.println("img

data size is :" + nSize);

data =newbyte[nSize];

inStream.read(data);

inStream.close();

}catch(IOException e) {

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(SQLException ex) {

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：

/**

*缩小或放大图片

*@paramdata图片的byte数据

*@paramw需要缩到的宽度

*@paramh需要缩到高度

*@return缩放后的图片的byte数据

*/

privatebyte[] ChangeImgSize(byte[] data,intnw,intnh){

byte[] newdata =null;

try{

BufferedImage

bis = ImageIO.read(newByteArrayInputStream(data));

intw = bis.getWidth();

inth = bis.getHeight();

doublesx = (double) nw / w;

doublesy = (double) nh / h;

AffineTransform transform =newAffineTransform();

transform.setToScale(sx, sy);

AffineTransformOp ato =newAffineTransformOp(transform,null);

//原始颜色

BufferedImage bid =newBufferedImage(nw, nh, BufferedImage.TYPE_3BYTE_BGR);

ato.filter(bis, bid);

//转换成byte字节

ByteArrayOutputStream baos =newByteArrayOutputStream();

ImageIO.write(bid,"jpeg", baos);

newdata = baos.toByteArray();

}catch(IOException

e){

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：

response.setContentType("image/jpeg");

//图片在数据库中的ID

String strID = request.getParameter("id");

//要缩略或放大图片的宽度

String strWidth = request.getParameter("w");

//要缩略或放大图片的高度

String strHeight = 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);

ServletOutputStream op = 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;

/*图片表名*/

privateStringstrTabName;

/*图片ID字段名*/

privateStringstrIDName;

/*图片字段名*/

privateStringstrImgName;

/**

*加载java连接Oracle的jdbc驱动

*/

publicOracleQueryBean(){

try{

Class.forName(oracleDriverName);

}catch(ClassNotFoundException ex){

System.out.println("加载jdbc驱动失败,原因:"+ ex.getMessage());

}

}

/**

*获取Oracle连接对象

*@returnConnection

*/

publicConnection getConnection(){

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

GetPara

oGetPara =newGetPara();

String

strIP = oGetPara.getPara("serverip");

String

strPort = oGetPara.getPara("port");

String

strDBName = oGetPara.getPara("dbname");

String

strUser = oGetPara.getPara("user");

String

strPassword = oGetPara.getPara("password");

this.strTabName=

oGetPara.getPara("tablename");

this.strIDName=

oGetPara.getPara("imgidname");

this.strImgName=

oGetPara.getPara("imgname");

String

oracleUrlToConnect ="jdbc:oracle:thin:@"+strIP+":"+strPort+":"+strDBName;

this.myConnection= DriverManager.getConnection(oracleUrlToConnect,

strUser, strPassword);

}catch(Exception ex){

System.out.println("Can not get connection:"+ 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;

}

/**

*根据图片在数据库中的ID进行读取

*@paramstrID图片字段ID

*@paramw需要缩到的宽度

*@paramh需要缩到高度

*@return缩放后的图片的byte数据

*/

publicbyte[] GetImgByteById(String strID,intw,inth){

//System.out.println("Get img data which id is

" + nID);

if(myConnection==null)

this.getConnection();

byte[] data =null;

try{

Statement stmt =myConnection.createStatement();

ResultSet myResultSet = stmt.executeQuery("select "+this.strIDName+" from "+this.strTabName+" where "+this.strIDName+"="+ strID);

StringBuffer myStringBuffer =newStringBuffer();

if(myResultSet.next()) {

java.sql.Blob blob = myResultSet.getBlob(this.strImgName);

InputStream inStream = blob.getBinaryStream();

try{

longnLen = blob.length();

intnSize = (int) nLen;

//System.out.println("img

data size is :" + nSize);

data =newbyte[nSize];

inStream.read(data);

inStream.close();

}catch(IOException e) {

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(SQLException ex) {

System.out.println(ex.getMessage());

}

returndata;

}

/**

*根据图片在数据库中的ID进行读取，显示原始大小的图片

*@paramstrID图片字段ID

*@return读取后的图片byte数据

*/

publicbyte[] GetImgByteById(String strID){

//System.out.println("Get img data which id is

" + nID);

if(myConnection==null)

this.getConnection();

byte[] data =null;

try{

Statement stmt =myConnection.createStatement();

ResultSet myResultSet = stmt.executeQuery("select "+this.strIDName+" from "+this.strTabName+" where "+this.strIDName+"="+ strID);

StringBuffer myStringBuffer =newStringBuffer();

if(myResultSet.next()) {

java.sql.Blob blob = myResultSet.getBlob(this.strImgName);

InputStream inStream = blob.getBinaryStream();

try{

longnLen = blob.length();

intnSize = (int) nLen;

data =newbyte[nSize];

inStream.read(data);

inStream.close();

}catch(IOException e) {

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(SQLException ex) {

System.out.println(ex.getMessage());

}

returndata;

}

/**

*缩小或放大图片

*@paramdata图片的byte数据

*@paramw需要缩到的宽度

*@paramh需要缩到高度

*@return

*/

privatebyte[] ChangeImgSize(byte[] data,intnw,intnh){

byte[] newdata =null;

try{

BufferedImage

bis = ImageIO.read(newByteArrayInputStream(data));

intw = bis.getWidth();

inth = bis.getHeight();

doublesx = (double) nw / w;

doublesy = (double) nh / h;

AffineTransform transform =newAffineTransform();

transform.setToScale(sx, sy);

AffineTransformOp ato =newAffineTransformOp(transform,null);

//原始颜色

BufferedImage bid =newBufferedImage(nw, nh, BufferedImage.TYPE_3BYTE_BGR);

ato.filter(bis, bid);

//转换成byte字节

ByteArrayOutputStream baos =newByteArrayOutputStream();

ImageIO.write(bid,"jpeg", baos);

newdata = baos.toByteArray();

}catch(IOException

e){

e.printStackTrace();

}

returnnewdata;

}

}