JAVA读取Oracle中的blob图片字段并显示

    技术2022-06-13  101

    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;

        }

    }

     

    本文来自博客,转载请标明出处:http://blog.csdn.net/pharaohsprince/archive/2009/10/12/4657837.aspx


    最新回复(0)