希望 stackoverflow 上的 Java 专家能够指点迷津:
我们通过序列化图像(将其转换为 Java ImageIcon Serialized 类型之后)成功发送图像，但序列化 IO 似乎很昂贵(readObject()、writeObject())，因为我们不断在 servlet 容器中遇到“java.lang.OutOfMemoryError: Java heap space”错误。
有没有更好的方法通过 HTTP 在 Java 中传输图像文件？
该应用程序使用 Java Robot 类通过 servlet 不断地将桌面图像发送到多个客户端(以促进 HTTP 传输)。 听起来已经是个好建议了，让我发布一些代码，让您对我的项目有一个想法。 我必须使用 Java(通过使用 servlet 的网络)，我的工作取决于此工作...请帮助...
__添加组件中的关键代码摘录___________
我。客户端小程序 (捕获桌面图像(通过套接字将序列化的图像发送到中央 ImageBroker)
-> 二．图像经纪人 (通过套接字从 ClientApplet 读取序列化图像并 将其发送到 servlet 以使其可供 HTTP 查看器小程序使用)
-> 三．查看器Servlet 通过 HTTP 将图像转发到小程序
-> IV.Applet读取序列化图像
// I. Client Applet
// (sends serialized desktop images to ImageBroker server over TCP sockets )
class ScreenShoot extends Thread {
Socket socket = null;
Robot robot = null; // Used to capture screen
Rectangle rectangle = null; //Used to represent screen dimensions
boolean continueLoop = true; //Used to exit the program
public ScreenShoot(Socket socket, Robot robot, Rectangle rect) {
this.socket = socket;
this.robot = robot;
rectangle = rect;
start();
}
public void run() {
ObjectOutputStream oos = null; //Used to write an object to the streem
try {
//Prepare ObjectOutputStream
oos = new ObjectOutputStream(socket.getOutputStream());
} catch (IOException ex) {
ex.printStackTrace();
}
String Userid = "test";
String ConfId = "ONE";
MyClass sendHeader = new MyClass(Userid,ConfId, 300, 300, 20, 30);
System.out.println("sendHeader: " + sendHeader);
// Send the header (username, ConferenceID) first before sending the images
try {
oos.writeObject(sendHeader);
System.out.println("sent HEADER object1: ");
} catch (IOException ex) {
ex.printStackTrace();
}
int countRec = 1;
while (continueLoop) {
//Capture screen
BufferedImage image = robot.createScreenCapture(rectangle);
/* I have to wrap BufferedImage with ImageIcon because BufferedImage class
* does not implement Serializable interface
*/
ImageIcon imageIcon = new ImageIcon(image);
//Send captured screen to the server
try {
System.out.println("ScreenSpyer:before sending image-writeObject");
// oos.writeObject(imageIcon);
oos.writeUnshared(imageIcon);
countRec++;
if (countRec > 20 ) {
oos.reset(); //Clear ObjectOutputStream cache
countRec = 1;
}
System.out.println("ScreenSpyer: New screenshot sent");
} catch (IOException ex) {
ex.printStackTrace();
}
//wait for 1000ms to redu/ e network traffic
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
II.Central ImageBroker 服务器 代理处理来自不同发送者的图像并将其传输给正确的查看者(通过 servlet) -通过 TCP 套接字从客户端 screensender 小程序接收图像 - 将序列化图像转发到 ViewerServlet
// Section READING the incoming images ( this is over simple TCP Sockets)
class HandleSenders extends Thread {
private Socket socket = null;
private WinTest mainprog;
private MessageBin source;
private InputStream fromServer = null;
public HandleSenders(WinTest mainprog, Socket socket, MessageBin source) {
super("HandleSenders");
this.socket = socket;
this.mainprog = mainprog;
this.source = source;
}
// getNextMessage() returns the next new message.
// It blocks until there is one.
public String getNextMessage() {
// Create a message sink to wait for a new message from the
// message source.
return new MessageHold().getNextMessage(source);
}
public void run() {
// Reading Images from SnreenSender client
ObjectInputStream in = null;
byte[] buffer = new byte[256];
int fromServer_val, backup_val =0 ;
try {
// in = new ObjectInputStream(socket.getInputStream());
fromServer = socket.getInputStream();
in = new ObjectInputStream(fromServer);
boolean forever = true;
int cntr = 1;
boolean contin = true;
int counter = 1;
boolean Found = false;
String theMessage = "";
while (contin) {
// if (cntr++ > 5) break;
// fromServer_val = fromServer.read(buffer);
// dealing with null values which crashes the system,
// if for some problem in transmission you get a null, we just put the
// previous valid data
// into the null one.
ImageIcon imageIcon = (ImageIcon)in.readObject();
Found = mainprog.FindViewersAndSend(senderHeader.confid, imageIcon);
// Blocks first time and only if the structure has no
// clients for this sender
if (!Found)
theMessage = getNextMessage(); //blocks
处理将图像发送到 servlet 的部分
public boolean FindViewersAndSend(String confid, ImageIcon imageIcon) {
Iterator it = socketMap.entrySet().iterator();
ObjectOutputStream viewerOut = null;
byte[] buffer = new byte[256];
Socket viewerClient = null;
OutputStream toClient = null;
boolean Found = false;
int recordCount = 1;
try {
while (it.hasNext()) {
// Iterating through structures of Viewer servlet socket connections
Map.Entry pairs = (Map.Entry)it.next();
socketUserStruct = getSocketDetails((String)pairs.getKey());
if ( socketUserStruct != null && !socketUserStruct.equals ("")) {
StructConfId = (String)socketUserStruct.getConfId();
StructUserId = (String)pairs.getKey();
}
if (StructConfId.equals(confid)) {
Found = true;
viewerOut = (ObjectOutputStream)socketUserStruct.getObjectOutputStream();
// write the serialized data to the servlet....
// which in turn sends it to the applet over http
// viewerOut.writeObject(imageIcon);
viewerOut.writeUnshared(imageIcon);
recordCount++;
if (recordCount > 10) {
viewerOut.flush();
recordCount = 0;
}
}
}
}
catch (IOException e)
{ /// clean up
removeSocketClient(StructUserId);
}
return Found;
}
<小时/>三． ViewerServlet - 从图像代理获取图像并将序列化图像发送到 Applet(通过 http)
public void doGet(HttpServletRequest req,
HttpServletResponse res) throws ServletException,
Socket echoSocket = null;
PrintWriter out = null;
InputStream fromServer = null;
byte[] buffer = new byte[256];
int fromServer_val, backup_val = 0;
// OutputStream toClient = res.getOutputStream();
try {
echoSocket = new Socket("localhost", RES_PORT);
out = new PrintWriter(echoSocket.getOutputStream(), true);
String screensize = "300";
String viewerHeader = userid+","+confid+","+screensize;
out.println(viewerHeader);
out.println("bye");
out.flush();
InputStream is = echoSocket.getInputStream();
ObjectInputStream in = new ObjectInputStream(is);
ObjectOutputStream oos = new ObjectOutputStream(res.getOutputStream());
try {
int recordCount = 1;
while (true) {
ImageIcon imageIcon = (ImageIcon)in.readObject();
oos.writeObject(imageIcon);
if (recordCount++ > 5) {
recordCount = 1;
oos.flush();
}
// oos.flush();
}
} catch (ClassNotFoundException e) {
.......
} catch (IOException ex) {
ex.printStackTrace();
}
} catch (IOException e) { // show("plainViewAdapter-doGet:4");
fromServer.close();
}
}
四。 Viewer Applet(连接到Viewer Servlet以接收图像)
public void start() {
try {
String url_string =
"http://" + winsellahost + ":" + winsellaport + "/BrowserShare
/viewerproxyservlet" +
"?userid=viewer1&confid=ONE";
URL url = new URL(url_string);
InputStream is = url.openConnection().getInputStream();
ObjectInputStream in = new ObjectInputStream(is);
boolean firstTime = true;
while (continueLoop) {
show("5");
//Recve client screenshot and resize it to the current panel size
ImageIcon imageIcon = (ImageIcon)in.readObject();
// in.reset();
Image image = imageIcon.getImage();
image =
image.getScaledInstance(cPanel.getWidth(), cPanel.getHeight(),
Image.SCALE_FAST);
//Draw the received screenshot
}
in.close();
is.close();
} catch (IOException ex) {
ex.printStackTrace();
} catch (ClassNotFoundException ex) {
ex.printStackTrace();
}
}
最佳答案
不要序列化为对象。
在 PNG 图像输出流中序列化 Bufferedimage，并从输入流的另一端读回它
使用 ImageIO.write 对其进行序列化，并使用 ImageIO.read 对其进行反序列化。
http://docs.oracle.com/javase/6/docs/api/javax/imageio/ImageIO.html
安东尼
关于java - 使用Java通过HTTP进行图像传输，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/9549301/