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JAVA读取Oracle中的blob图片字段并显示(转)  

2011-10-25 23:52:06|  分类: Web开发 |  标签: |举报 |字号 订阅

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转自:http://www.blogjava.net/zhangqingping/articles/JAVA.html
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Oraclejdbc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

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

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Oraclejdbc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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