JAVA读取Oracle中的blob图片字段并显示 -

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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：
<h1>
1. java连接Oracle</h1>
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: 
<a href="http://www.oracle.com/technology/software/tech/java/sqlj_jdbc/htdocs/jdbc101040.html">http://www.oracle.com/technology/software/tech/java/sqlj_jdbc/htdocs/jdbc101040.html</a> 

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;
 }
}

<h1>
2. 读取blob字段
</h1>

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;
}


<h1>
3. 缩放图片
</h1>
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;
}

<h1>
4. 展示在页面
</h1>
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" class="HLFtiDemo.OracleQueryBean" />
<%
 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();
 }
%>


<h1>
5. OracleQueryBean查询类的整体代码
</h1>
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;
 }
}

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