JSP上传图片并生成缩略图

JSP上传图片并生成缩略图

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本例子使用了jspsmart组件进行上传，这里可以免费下载该组件www.jspsmart.com
下载解压后，将jar包复制到　/WEB-INF/lib　目录后重启服务器，jspsmart即可正常使用了

1、uploadimage.jsp

<%@ page contentType='text/html;charset=gb2312' language='java' import='java.io.*,java.awt.Image,java.awt.image.*,com.sun.image.codec.jpeg.*,
java.sql.*,com.jspsmart.upload.*,java.util.*,cn.oof.database.*,cn.oof.house.*'%>
<%
SmartUpload mySmartUpload =new SmartUpload();
long file_size_max=4000000;
String fileName2='',ext='',testvar='';
String url='uploadfile/images/';      //应保证在根目录中有此目录的存在
//初始化
mySmartUpload.initialize(pageContext);
//只允许上载此类文件
try {
 mySmartUpload.setAllowedFilesList('jpg,gif');
//上载文件
 mySmartUpload.upload();
} catch (Exception e){
%>
  <SCRIPT language=javascript>
  alert('只允许上传.jpg和.gif类型图片文件');
  window.location='upfile.jsp';
  </script>
<%
}
try{

    com.jspsmart.upload.File myFile = mySmartUpload.getFiles().getFile(0);
    if (myFile.isMissing()){%>
   <SCRIPT language=javascript>
   alert('请先选择要上传的文件');
   window.location='upfile.jsp';
   </script>
    <%}
    else{
      //String myFileName=myFile.getFileName(); //取得上载的文件的文件名
   ext= myFile.getFileExt();      //取得后缀名
   int file_size=myFile.getSize();     //取得文件的大小 
   String saveurl='';
   if(file_size<file_size_max){
    //更改文件名，取得当前上传时间的毫秒数值
    Calendar calendar = Calendar.getInstance();
    String filename = String.valueOf(calendar.getTimeInMillis());
    saveurl=request.getRealPath('/')+url;
    saveurl+=filename+'.'+ext;          //保存路径
    myFile.saveAs(saveurl,mySmartUpload.SAVE_PHYSICAL);
    //out.print(filename);
//-----------------------上传完成，开始生成缩略图-------------------------   
    java.io.File file = new java.io.File(saveurl);        //读入刚才上传的文件
    String newurl=request.getRealPath('/')+url+filename+'_min.'+ext;  //新的缩略图保存地址
    Image src = javax.imageio.ImageIO.read(file);                     //构造Image对象
    float tagsize=200;
    int old_w=src.getWidth(null);                                     //得到源图宽
    int old_h=src.getHeight(null);  
    int new_w=0;
    int new_h=0;                            //得到源图长
    int tempsize;
    float tempdouble;
    if(old_w>old_h){
     tempdouble=old_w/tagsize;
    }else{
     tempdouble=old_h/tagsize;
    }
    new_w=Math.round(old_w/tempdouble);
    new_h=Math.round(old_h/tempdouble);//计算新图长宽
    BufferedImage tag = new BufferedImage(new_w,new_h,BufferedImage.TYPE_INT_RGB);
    tag.getGraphics().drawImage(src,0,0,new_w,new_h,null);       //绘制缩小后的图
    FileOutputStream newimage=new FileOutputStream(newurl);          //输出到文件流
    JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(newimage);      
    encoder.encode(tag);                                               //近JPEG编码
     newimage.close();   

   }
   else{
    out.print('<SCRIPT language='javascript'>');
    out.print('alert('上传文件大小不能超过'+(file_size_max/1000)+'K');');
    out.print('window.location='upfile.jsp;'');
    out.print('</SCRIPT>');
   }
  }
}catch (Exception e){

e.toString();

}
%>

2 upload.htm
<html>
<head>
<title>请选择上传的图片</title>
</head>
<body>
<table border='0' align='center' cellpadding='0' cellspacing='0'>
  <tr>
    <td height='45' align='center' valign='middle'><form action='uploadimage.jsp' method='post' enctype='multipart/form-data' name='form1'>
请选择上传的图片
    <input type='file' name='file'>
<input type='submit' name='Submit' value='上传'>
    </form></td>
  </tr>
</table>
</body>
</html>