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:

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" 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();
    }
%>
 
 
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;
    }
}