Java从数据库中读取Blob对象图片并显示的方法
本文实例讲述了java从数据库中读取blob对象图片并显示的方法。分享给大家供大家参考。具体实现方法如下：
第一种方法：
大致方法就是，从数据库中读出blob的流来，写到页面中去：
string sql = "select picture from teacher where id=1";
preparedstatement ps = null;
resultset rs = null;
inputstream is = null;
outputstream os = null;
try {
ps = conn.preparestatement(sql);
rs = ps.executequery();
if(rs.next()){
is = rs.getbinarystream(1);
}
response.setcontenttype("text/html");
os = response.getoutputstream();
int num;
byte buf[] = new byte[1024];
while( (num=is.read(buf))!=-1 ){
os.write(buf, 0, num);
}
} catch (sqlexception e) {
e.printstacktrace();
}
try {
is.close();
os.close();
rs.close();
ps.close();
} catch (sqlexception e) {
e.printstacktrace();
}
在页面中：
string path = request.getcontextpath();
string basepath = request.getscheme()+"://"+request.getservername()+":"+request.getserverport()+path+"/";
%>
<img name="pic" src="<%=basepath+"servlet/downloadasstream"%>"/>
搞定。
第二种方法：
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。
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;
private string strtabname;
private string stridname;
private string strimgname;
public oraclequerybean(){
try{
class.forname(oracledrivername);
}catch(classnotfoundexception ex){
system.out.println("加载jdbc驱动失败,原因:" + ex.getmessage());
}
}
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：
//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：
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：
<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.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;
private string strtabname;
private string stridname;
private string strimgname;
public oraclequerybean(){
try{
class.forname(oracledrivername);
}catch(classnotfoundexception ex){
system.out.println("加载jdbc驱动失败,原因:" + ex.getmessage());
}
}
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;
}
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;
}
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;
}
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;
}
}
下面是我的存储读取blob图片的案例
import java.io.*;
public class insertphoto {
public static void main(string[] args) throws exception{
class.forname("com.mysql.jdbc.driver");
connection con = drivermanager.getconnection("jdbc:mysql://127.0.0.1/wiseweb?user=root&password=root");
file f = new file("e:/123.jpg");
fileinputstream fis = new fileinputstream(f);
string sql = "insert into photo(photo,photoname) values(?,?)";
preparedstatement pstmt = con.preparestatement(sql);
pstmt.setbinarystream(1,fis,(int)f.length());
pstmt.setstring(2, "测试图片");
pstmt.executeupdate();
fis.close();
pstmt.close();
con.close();
}
}
import java.io.bufferedinputstream;
import java.io.ioexception;
import java.io.inputstream;
import java.io.outputstream;
import java.sql.connection;
import java.sql.drivermanager;
import java.sql.resultset;
import java.sql.sqlexception;
import java.sql.statement;
import javax.imageio.imageio;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import com.sun.image.codec.jpeg.jpegcodec;
import com.sun.image.codec.jpeg.jpegimageencoder;
public class readphoto extends httpservlet{
private static final long serialversionuid = 1l;
public void doget(httpservletrequest request, httpservletresponse response){
if(request.getparameter("id") != null){
response.setcontenttype("image/jpeg");
try {
inputstream is = query_getphotoimageblob(integer.parseint(request.getparameter("id"))) ;
if(is != null){
is = new bufferedinputstream(is) ;
bufferedimage bi = imageio.read(is) ;
outputstream os = response.getoutputstream() ;
jpegimageencoder encoder = jpegcodec.createjpegencoder(os) ;
encoder.encode(bi);
os.close();
is.close();
}
} catch(ioexception e){
e.printstacktrace();
}catch (numberformatexception e) {
// todo auto-generated catch block
e.printstacktrace();
} catch (classnotfoundexception e) {
// todo auto-generated catch block
e.printstacktrace();
} catch (sqlexception e) {
// todo auto-generated catch block
e.printstacktrace();
}
}
}
public static inputstream query_getphotoimageblob(int id) throws classnotfoundexception, sqlexception{
string sql = "select photo from photo where id="+id;
connection con = null;
statement stmt = null;
resultset rs = null;
inputstream result = null;
try {
class.forname("com.mysql.jdbc.driver");
con = drivermanager.getconnection("jdbc:mysql://127.0.0.1/wiseweb?user=root&password=root");
stmt = con.createstatement();
rs = stmt.executequery(sql);
if (rs.next())
result = rs.getblob("photo").getbinarystream();
} catch (sqlexception e) {
// todo: handle exception
system.err.println(e.getmessage());
}finally{
rs.close();
stmt.close();
con.close();
}
return result;
}
}
jsp显示
web.xml中配置
<servlet-name>genimage</servlet-name>
<servlet-class>readphoto</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>genimage</servlet-name>
<url-pattern>/genimage</url-pattern>
</servlet-mapping>
希望本文所述对大家的java程序设计有所帮助。