整個流程分爲四步，連接oracle數據庫 -> 讀取blob圖片字段 -> 對圖片進行縮放 ->把圖片展示在jsp頁面上。
下面進行詳細描述：
1. java連接Oracle
注：數據庫是Oracle10g版本爲10.2.0, 在數據庫中，圖片字段類型爲BLOB。
java中通常使用的是通過jdbc驅動來連接數據庫，oracle也不例外，因此必須下載一個Oracle驅動的jdbc需要去網上進行下載,名稱爲 ojdbc14.jar。
下載地址爲:
http://www.oracle.com/technology/software/tech/java/sqlj_jdbc/htdocs/jdbc101040.html
下載了驅動之後，可以使用驅動裏提供的接口進行連接，具體代碼如下：
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;
/*圖片表名*/
private String strTabName;
/*圖片ID字段名*/
private String strIDName;
/*圖片字段名*/
private String strImgName;
/**
* 加載java連接Oracle的jdbc驅動
*/
public OracleQueryBean(){
try{
Class.forName(oracleDriverName);
}catch(ClassNotFoundException ex){
System.out.println("加載jdbc驅動失敗,原因:" + ex.getMessage());
}
}
/**
* 獲取Oracle連接對象
* @return Connection
*/
public Connection getConnection(){
try{
//用戶名+密碼; 以下使用的Test就是Oracle裏的表空間
//從配置文件中讀取數據庫信息
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("請檢測配置文件中的數據庫信息是否正確." );
}
return this.myConnection;
}
}
2. 讀取blob字段
在OracleQueryBean類中增加一個函數，來進行讀取，具體代碼如下：
/**
* 根據圖片在數據庫中的ID進行讀取
* @param strID 圖片字段ID
* @param w 需要縮到的寬度
* @param h 需要縮到高度
* @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("獲取圖片數據失敗,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. 縮放圖片
因爲圖片的大小可能不一致，但是在頁面中輸出的大小需要統一，所以需要
在OracleQueryBean類中增加一個函數，來進行縮放，具體代碼如下：
/**
* 縮小或放大圖片
* @param data 圖片的byte數據
* @param w 需要縮到的寬度
* @param h 需要縮到高度
* @return 縮放後的圖片的byte數據
*/
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);
//原始顏色
BufferedImage bid = new BufferedImage(nw, nh, BufferedImage.TYPE_3BYTE_BGR);
ato.filter(bis, bid);
//轉換成byte字節
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(bid, "jpeg", baos);
newdata = baos.toByteArray();
}catch(IOException e){
e.printStackTrace();
}
return newdata;
}
4. 展示在頁面
頁面使用OracleQueryBean來根據用戶提供的圖片id進行查詢，在讀取並進行縮放後，通過jsp頁面進行展示，具體代碼如下：
<%@ page language="java" contentType="text/html;;charset=gbk" %>
<jsp:useBean id="OrcleQuery" scope="page" class="HLFtiDemo.OracleQueryBean" />
<%
response.setContentType("image/jpeg");
//圖片在數據庫中的 ID
String strID = request.getParameter("id");
//要縮略或放大圖片的寬度
String strWidth = request.getParameter("w");
//要縮略或放大圖片的高度
String strHeight = request.getParameter("h");
byte[] data = null;
if(strID != null){
int nWith = Integer.parseInt(strWidth);
int nHeight = Integer.parseInt(strHeight);
//獲取圖片的byte數據
data = OrcleQuery.GetImgByteById(strID, nWith, nHeight);
ServletOutputStream op = response.getOutputStream();
op.write(data, 0, data.length);
op.close();
op = null;
response.flushBuffer();
//清除輸出流，防止釋放時被捕獲異常
out.clear();
out = pageContext.pushBody();
}
%>
5. OracleQueryBean查詢類的整體代碼
OracleQueryBean.java文件代碼如下所示：
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;
/*圖片表名*/
private String strTabName;
/*圖片ID字段名*/
private String strIDName;
/*圖片字段名*/
private String strImgName;
/**
* 加載java連接Oracle的jdbc驅動
*/
public OracleQueryBean(){
try{
Class.forName(oracleDriverName);
}catch(ClassNotFoundException ex){
System.out.println("加載jdbc驅動失敗,原因:" + ex.getMessage());
}
}
/**
* 獲取Oracle連接對象
* @return Connection
*/
public Connection getConnection(){
try{
//用戶名+密碼; 以下使用的Test就是Oracle裏的表空間
//從配置文件中讀取數據庫信息
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("請檢測配置文件中的數據庫信息是否正確." );
}
return this.myConnection;
}
/**
* 根據圖片在數據庫中的ID進行讀取
* @param strID 圖片字段ID
* @param w 需要縮到的寬度
* @param h 需要縮到高度
* @return 縮放後的圖片的byte數據
*/
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("獲取圖片數據失敗,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;
}
/**
* 根據圖片在數據庫中的ID進行讀取，顯示原始大小的圖片
* @param strID 圖片字段ID
* @return 讀取後的圖片byte數據
*/
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("獲取圖片數據失敗,原因:" + e.getMessage());
}
}
System.out.println(myStringBuffer.toString());
myConnection.commit();
myConnection.close();
} catch (SQLException ex) {
System.out.println(ex.getMessage());
}
return data;
}
/**
* 縮小或放大圖片
* @param data 圖片的byte數據
* @param w 需要縮到的寬度
* @param h 需要縮到高度
* @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);
//原始顏色
BufferedImage bid = new BufferedImage(nw, nh, BufferedImage.TYPE_3BYTE_BGR);
ato.filter(bis, bid);
//轉換成byte字節
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(bid, "jpeg", baos);
newdata = baos.toByteArray();
}catch(IOException e){
e.printStackTrace();
}
return newdata;
}
}
