我的servlet通过我的JSP页面为提交上传的文件执行以下操作。
第1步 - 获取文件，它始终是图像
第2步 - 检查是否需要调整大小
步骤2a - 如果需要调整大小，请执行此操作
第3步 - 同时调整大小并创建缩略图大小
步骤4 - 将新调整大小的图像存储在服务器上的文件夹中
步骤5 - 将缩略图图像存储在服务器上的文件夹中
servlet接受处理的最大图像大小（按照我的客户要求）是3900 x 3900 ......我知道，这是巨大的！但这就是客户想要的。
我已经将servlet放在我的vps上的tomcat上进行测试，我看到一些非常严重的内存消耗。
VPS内存限制
我得到316MB的内存。随着Tomcat重新启动，内存大约为108MB。 VPS也在运行Apache服务器。
Apache ，Tomcat STOPPED使用45MB，因此Tomcat在初次启动时占用63MB。
Tomcat.conf - 文件具有以下针对堆的设置。
# Initial Java Heap Size (in MB)
wrapper.java.initmemory=100
# Maximum Java Heap Size (in MB)
wrapper.java.maxmemory=128
一旦我运行图像上传过程 - 通过JSP页面上的表单提交图像文件 - servlet就会从那里接管上面描述的步骤。
我使用相同的图像来测试。图像大小为3872 x 2592像素，相当于2.53MB。
我提交此图片约5次。每次上传最多需要一分钟或更长时间才能完成。
1张图片：记忆= 150mb
2图像：内存= 179mb
3图像：179.8
4图像：188.8
5图像：189.3
为什么在上传仅2.53MB的图片后出现这样的跳转？ 我不明白。当内存下降时，它会略微下降。我在前5个之后上传了另一张图片，内存转到了188.8。
我的代码是否存在效率低下的问题？我确保关闭所有流，或者至少我很确定我做了。
非常感谢任何输入。
public void addPhoto(Statement stmt, HttpServletRequest req, HttpServletResponse res, HttpSession session) {
BufferedInputStream bis = null;
BufferedImage bufimg = null;
BufferedImage resized = null;
ByteArrayOutputStream bytestream = null;
BufferedOutputStream bos = null;
FileOutputStream fos = null;
try {
String ImageMain = "";
String ImageThumb = "";
String dbShortPathMain = "images/gallery/";
String dbShortPathThumb = "images/gallery/";
String fileNameToLowerCase = "";
String fileExtension = "";
byte[] newimage = null;
boolean isPart = ServletFileUpload.isMultipartContent(req);
if(isPart) {
FileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload fileupload = new ServletFileUpload(factory);
java.util.List items = fileupload.parseRequest(req);
Iterator it = items.iterator();
while(it.hasNext()) { //while1
FileItem item = (FileItem)it.next();
String fieldValue = item.getName();
if(!item.isFormField()) {
String fieldName = item.getFieldName();
if(fieldName.equals("ImageMain")) { //10
//--------------------------
//continue processing upload
//field wasn't blank
//---------------------------
// Create a FileItem object to access the file.
File f = new File(fieldValue);
// Get content type by filename.
String contentType = getServletContext().getMimeType(f.getName());
if(contentType == null) contentType = "none";
if(!contentType.startsWith("image")) {
appendToURL += "¬file=y";
} else {
//check size
bis = new BufferedInputStream(item.getInputStream());
//BufferedImage
bufimg = ImageIO.read(bis);
//check size of image
int img_width = bufimg.getWidth();
int img_height = bufimg.getHeight();
//not accepting images larger than 3900 x 3900
if(img_width > 3900 || img_height > 3900) {
appendToURL += "&filesize=y";
} else {
//------------------------------------------
// R E S I Z E & U P L O A D F I L E
//------------------------------------------
//#### STEP 1 - make size (600 max width) image ####
double scale = (double)maxLargeImageSize/(double)img_width;
Image sized = getScaledInstanceAWT(bufimg, scale, Image.SCALE_SMOOTH);
//convert image to BufferedImage
resized = toBufferedImage(sized, BufferedImage.TYPE_INT_RGB);
bytestream = new ByteArrayOutputStream();
//make file name characters all lowercase, and extract extension (.jpg)
fileNameToLowerCase = fieldValue.toLowerCase();
fileExtension = fileNameToLowerCase.substring(fileNameToLowerCase.indexOf(".")+1,fileNameToLowerCase.length());
//initialize buffer output stream for efficiency
//BufferedOutputStream
bos = new BufferedOutputStream(bytestream);
//W R I T E image to BufferedOutputStream and ByteArrayOutputStream
if(fileExtension.equals("png"))
ImageIO.write(resized,"png",bos);
if(fileExtension.equals("jpg"))
ImageIO.write(resized,"jpg",bos);
if(fileExtension.equals("jpeg"))
ImageIO.write(resized,"jpeg",bos);
if(fileExtension.equals("gif"))
ImageIO.write(resized,"gif",bos);
if(fileExtension.equals("bmp"))
ImageIO.write(resized,"bmp",bos);
// Flush ByteArrayOutputStream
bytestream.flush();
//convert the bytes in stream to byte array
//byte[]
newimage = bytestream.toByteArray();
//specify the file name
ImageMain = FileUploadPath+"/thenewfile."+fileExtension;
dbShortPathMain += cat+"/thenewfile."+fileExtension;
fos = new FileOutputStream(ImageMain);
fos.write(newimage);
fos.flush();
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//#### STEP 2 - make Thumb size (140 max width) image ####
scale = (double)maxThumbImageSize/(double)img_height;
sized = getScaledInstanceAWT(bufimg, scale, Image.SCALE_SMOOTH);
//convert image to BufferedImage
resized = toBufferedImage(sized, BufferedImage.TYPE_INT_RGB);
//used to convert the new image to bytes so it can be put into db
//ByteArrayOutputStream
bytestream = new ByteArrayOutputStream();
//initialize buffer output stream for efficiency
//BufferedOutputStream
bos = new BufferedOutputStream(bytestream);
//W R I T E image to BufferedOutputStream and ByteArrayOutputStream
if(fileExtension.equals("png"))
ImageIO.write(resized,"png",bos);
if(fileExtension.equals("jpg"))
ImageIO.write(resized,"jpg",bos);
if(fileExtension.equals("jpeg"))
ImageIO.write(resized,"jpeg",bos);
if(fileExtension.equals("gif"))
ImageIO.write(resized,"gif",bos);
if(fileExtension.equals("bmp"))
ImageIO.write(resized,"bmp",bos);
// Flush ByteArrayOutputStream
bytestream.flush();
//convert the bytes in stream to byte array
//byte[]
newimage = bytestream.toByteArray();
//specify the file name
ImageThumb = FileUploadPath+"/newfilethumb."+fileExtension;
dbShortPathThumb += cat+"/newfilethumb."+fileExtension;
fos = new FileOutputStream(ImageThumb);
fos.write(newimage);
fos.flush();
//#### end large size ####
//---------------------------------------
}
}
}
}//isFormField
}//while
}//isPart
}//try
catch(Exception e) {}
finally {
if (bis != null) try { bis.close(); } catch (IOException logOrIgnore) {}
if (bytestream != null) try { bytestream.close(); } catch (IOException logOrIgnore) {}
if (bos != null) try { bos.close(); } catch (IOException logOrIgnore) {}
if (fos != null) try { fos.close(); } catch (IOException logOrIgnore) {}
}
}//addPhoto
//-----------------------------------------------------------
//R E S I Z I N G I M A G E M E T H O D S
//-----------------------------------------------------------
public BufferedImage toBufferedImage(Image image, int type) {
BufferedImage result = null;
try {
int w = image.getWidth(null);
int h = image.getHeight(null);
result = new BufferedImage(w, h, type);
Graphics2D g = result.createGraphics();
g.drawImage(image, 0, 0, null);
g.dispose();
}//try
catch(Exception e) {}
return result;
}//end
public Image getScaledInstanceAWT(BufferedImage source, double scale, int hint) {
Image newimage = null;
try {
int w = (int) (source.getWidth() * scale);
int h = (int) (source.getHeight() * scale);
newimage = source.getScaledInstance(w, h, hint);
}//try
catch(Exception e) {}
return newimage;
}//end