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：
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:
http://www.oracle.com/technology/software/tech/java/sqlj_jdbc/htdocs/jdbc101040.html
?
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：
import java.sql.*;import java.io.*; import javax.imageio.ImageIO;import java.awt.image.BufferedImage;import java.awt.image.AffineTransformOp;import java.awt.geom.AffineTransform; public class OracleQueryBean { private final String oracleDriverName = "oracle.jdbc.driver.OracleDriver"; private Connection myConnection = null; /*图片表名*/ private String strTabName; /*图片ID字段名*/ private String strIDName; /*图片字段名*/ private String strImgName; /** * 加载java连接Oracle的jdbc驱动 */ public OracleQueryBean(){ 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 * @return Connection */ public Connection 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 = new GetPara(); 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." ); } return this.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 * @param strID 图片字段ID * @param w 需要缩到的宽度 * @param h 需要缩到高度 * @return */ public byte[] GetImgByteById(String strID, int w, int h){ //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 = new StringBuffer(); if (myResultSet.next()) { java.sql.Blob blob = myResultSet.getBlob(this.strImgName); InputStream inStream = blob.getBinaryStream(); try { long nLen = blob.length(); int nSize = (int) nLen; //System.out.println("img data size is :" + nSize); data = new byte[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()); } return data;} 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 * @param data 图片的byte数据 * @param w 需要缩到的宽度 * @param h 需要缩到高度 * @return 缩放后的图片的byte数据 */ private byte[] ChangeImgSize(byte[] data, int nw, int nh){ byte[] newdata = null; try{ BufferedImage bis = ImageIO.read(new ByteArrayInputStream(data)); int w = bis.getWidth(); int h = bis.getHeight(); double sx = (double) nw / w; double sy = (double) nh / h; AffineTransform transform = new AffineTransform(); transform.setToScale(sx, sy); AffineTransformOp ato = new AffineTransformOp(transform, null); //原始颜色 BufferedImage bid = new BufferedImage(nw, nh, BufferedImage.TYPE_3BYTE_BGR); ato.filter(bis, bid); //转换成byte字节 ByteArrayOutputStream baos = new ByteArrayOutputStream(); ImageIO.write(bid, "jpeg", baos); newdata = baos.toByteArray(); }catch(IOException e){ e.printStackTrace(); } return newdata;} 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： <%@ page language="java" contentType="text/html;;charset=gbk" %><jsp:useBean id="OrcleQuery" scope="page" /><% 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){ int nWith = Integer.parseInt(strWidth); int nHeight = 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： import java.sql.*;import java.io.*; import javax.imageio.ImageIO;import java.awt.image.BufferedImage;import java.awt.image.AffineTransformOp;import java.awt.geom.AffineTransform; public class OracleQueryBean { private final String oracleDriverName = "oracle.jdbc.driver.OracleDriver"; private Connection myConnection = null; /*图片表名*/ private String strTabName; /*图片ID字段名*/ private String strIDName; /*图片字段名*/ private String strImgName; /** * 加载java连接Oracle的jdbc驱动 */ public OracleQueryBean(){ 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 * @return Connection */ public Connection 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 = new GetPara(); 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." ); } return this.myConnection; } /** * 根据图片在数据库中的ID进行读取 * @param strID 图片字段ID * @param w 需要缩到的宽度 * @param h 需要缩到高度 * @return 缩放后的图片的byte数据 */ public byte[] GetImgByteById(String strID, int w, int h){ //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 = new StringBuffer(); if (myResultSet.next()) { java.sql.Blob blob = myResultSet.getBlob(this.strImgName); InputStream inStream = blob.getBinaryStream(); try { long nLen = blob.length(); int nSize = (int) nLen; //System.out.println("img data size is :" + nSize); data = new byte[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()); } return data; } /** * 根据图片在数据库中的ID进行读取，显示原始大小的图片 * @param strID 图片字段ID * @return 读取后的图片byte数据 */ public byte[] 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 = new StringBuffer(); if (myResultSet.next()) { java.sql.Blob blob = myResultSet.getBlob(this.strImgName); InputStream inStream = blob.getBinaryStream(); try { long nLen = blob.length(); int nSize = (int) nLen; data = new byte[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()); } return data; } /** * 缩小或放大图片 * @param data 图片的byte数据 * @param w 需要缩到的宽度 * @param h 需要缩到高度 * @return */ private byte[] ChangeImgSize(byte[] data, int nw, int nh){ byte[] newdata = null; try{ BufferedImage bis = ImageIO.read(new ByteArrayInputStream(data)); int w = bis.getWidth(); int h = bis.getHeight(); double sx = (double) nw / w; double sy = (double) nh / h; AffineTransform transform = new AffineTransform(); transform.setToScale(sx, sy); AffineTransformOp ato = new AffineTransformOp(transform, null); //原始颜色 BufferedImage bid = new BufferedImage(nw, nh, BufferedImage.TYPE_3BYTE_BGR); ato.filter(bis, bid); //转换成byte字节 ByteArrayOutputStream baos = new ByteArrayOutputStream(); ImageIO.write(bid, "jpeg", baos); newdata = baos.toByteArray(); }catch(IOException e){ e.printStackTrace(); } return newdata; }}?