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Again, Problem or Bug for URLConnection ?

Dedian — Fri, 20 Oct 2006 23:20:00 GMT

Not sure if it is a bug of (Http)URLConnection, but it hang sometimes for some URLs while calling any functions to get information from connection (includes getResponseCode, getInputStream, getContent, getContentLength, getHeaderField blabla..) after connection has been built (even I have set the read timeout and connect time out).

the functions openConnection() and connect() are ok, curious about that problem.

anybody has the same problem or similar problem with URLConnection?

Dedian 2006-10-21 07:20 发表评论

Ajax ��谈

Dedian — Fri, 06 Oct 2006 23:05:00 GMT

---��大家中�U�愉�?--

Ajax (Asynchronous JavaScript and XML)是近�q�来��行的一门web 技术。在Blogjava上看到有人开始在介绍AJAX�Q�但仿佛��于概念或理论的东西�Q�对于想用Ajax的初学者似乎不是很make sense。我惻I��学习��M��一��h��的技术，例子和步骤是极�ؓmake sense的两样东�ѝ�?br />
�W�者想�l�合�q�去的学习经验简单讲讲��用Ajax的基本步骤和丑և�个实用例子。由于笔者主要在于后台端的开发，所以很多脚本�ƈ不是很擅�ѝ��Ajax也主要限于以前大学的修课和近期的一些�ؓ后台端程序的��试的简单实现。所以只是一个抛砖引玉的使用Ajax版本�Q�欢�q�相互学习交��?br />
0. ��D��

    1。��用Ajax的基本流�E?br />    2。��用Ajax的基本步骤�?��单例�?-> Demo)
    3�?/b>再来一个例�?Google Suggest)�?Demo)
    4。家庭作�?:)

1。��用Ajax的基本流�E?/b>

在笔者看来，Ajax更像是一个简单的�|�络框架�Q�它描述着如何高效��C�ɾ|�络前端的数据展现和�|�络后端的数据之间的交互。基本上�Q�就是浏览器提供一个XMLHttpRequest(当然在IE里是ActiveXObject)的对象向后台端的脚本�E�序或者Servlet Classes发送http��h��Q�从后台端的回应中获取文本数�?如xml格式和最�q�有��论的Json格式)�q�嵌入前台段的网��中或脚本中�?br />
下图是一个简单的��程图：

2。��用Ajax的基本步骤�?/b>

下面�Q�我们结合上面的��程�Q�以及一个简单的例子(�?a >�q�篇文章)�q�一遍基本的步骤�?蓝色代码为标准写�?

�W�一步：Form 代码�Q�接受前台端的输入，�q��过Action�Ҏ��(�Ҏ��函数里包含创建XMLHttpRequest对象)把request post到后台端�?br />
onblur="checkName(this.value,'')" />

This name is in use, please try another.

注：
1�?�q�里的form只是一个input box,action的方法是onblur,��是响应失去焦点的事�Ӟ��然后调用一个函数checkName, �q�个函数里通过XMLHttpRequest向PHP server script 发送Post��h��(看得出来�Q�这里的php server script的文件名叫checkUserName.php�Q�唯一参数是q)�?br />2。函数loadXMLDoc里有个通用的创建XMLHttpRequest对象的代码，标准代码整理如下�Q?br />        var req;
        function foo()
        {
            req = false;

            // branch for native XMLHttpRequest object
            if(window.XMLHttpRequest)
            {
                try
                {
                    req = new XMLHttpRequest();
                }
                catch(e)
                {
                    req = false;
                }
            }
            else if(window.ActiveXObject) // branch for IE/Windows ActiveX version
            {
                try
                {
                    req = new ActiveXObject("Msxml2.XMLHTTP");
                }
                catch(e)
                {
                    try
                    {
                        req = new ActiveXObject("Microsoft.XMLHTTP");
                    }
                    catch(e)
                    {
                        req = false;
                    }
                }
            }
            if(req)
            {
                  //do something here
             }


        }

�W�二步：响应文本处理代码�Q�XMLHttpRequest对象里有个类似消息响应函数的属性，即通过讄�� req.onreadystatechange 来告诉XMLHttpRequest在哪个函数里处理服务端返回的文本信息�?br />如在上面的例子中�Q?br />
req.onreadystatechange = processReqChange;
那么我们接着要有一个processReqChange的函敎ͼ�
function processReqChange() { // only if req shows "complete" if (req.readyState == 4) { // only if "OK" if (req.status == 200) { // ...processing statements go here... processResponse(); } else { alert("There was a problem retrieving the XML data:\n" + req.statusText); } } } function processResponse() { response = req.responseXML.documentElement; method = response.getElementsByTagName('method')[0].firstChild.data; result = response.getElementsByTagName('result')[0].firstChild.data; eval(method + '(\'\', result)'); }
注：
1�?基本�?code>processReqChange 函数是标准代码的写法�?br />2。这里要用到前面定义的全局变量(XMLHttpRequest对象)req

�W�三步：后台端代�?�q�个例子是php server script)�Q�接受前台端的请求，处理其参敎ͼ��q�返回相应的�l�果�?br />
文�g�? checkUserName.php

header('Content-Type: text/xml');

function nameInUse($q)
{
if (isset($q)){
    switch(strtolower($q))
    {
      case 'drew' :
          return '1';
          break;
      case 'fred' :
          return '1';
          break;
      default:
          return '0';
    }
}else{
    return '0';
}

}
?>
'; ?>

checkName
    echo nameInUse($_GET['q']) ?>

注：代码很简单，��׃��用解释了。这里返回的是xml格式的字�W�串�?br />
��M��效果�?a >�q�里
输入"fred"或�?drew"的名字，失去焦点后会昄��名字已存在的信息�?br />

3。再来一个例子�?/b>

�q�里再讲一个实用的例子�Q�这是以前上评��一个课堂作业，也很有代表性。是关于Google Suggest(好像新的Google Toolbar上就用的�q�个功能)的应用问题。这里是写好�?a >DEMO。现在越来越多的�|�站提供�c�M��Web Service的API, 我们利用他们提供的API URL可以�q�回一些我们用的着的数据，攑֜�我们的网��上。这里就用的上Ajax。只不过有些�q�回来的文本数据是xml格式的，��可以利用上面的��单例子来处理�Q�但很多像Google Suggest那样是返回一�D늱��g��码格式的文本。我们就要利用Javascript的eval函数�Q�把�q�些文本当作一�D�代码在嵌入自己的网��中。如果嵌入的代码中含有函敎ͼ�则需要自己再写一个同名的函数作�ؓ实现�?�q�就是流�E�图中的optional的func 3)

�q�里完整代码��׃��贴了�Q�脓一些关键代�?原本后台端是用Java Servlet写的�Q�但做demo的空间没有Tomcat不支持Servlet,所以改用Php实现�Q�大家可以自��q��Java再写一边作为家庭作�?:) )�Q?br />
1) form 代码�Q?br />



        Search Term:






results go here . . .



注：
a. 看得出来�Q�要把查询的字符串post到google_suggest.php�?br />b. action的函数是GetSuggestion()�Q�其�q�回的字�W�串会显�C�在预留的网��늩�间里�?br />
2) 后台端代�?PHP)�Q�这里主要接收前台的��h��Q��ƈ不请求�{化�ؓ向Google Suggest的API URL��h��Q�把接收到的文本信息�q�回�l�前端。代码很��单，如下�Q?br />
文�g名：google_suggest.php

function getGoogleSuggest($q)
{

    $url = "http://www.google.com/complete/search?hl=en&js=true&qu=" . $q;
    return file_get_contents($url);
}
?>

注：
a�?Google Suggest API �q�回的是一个代码格式的文本信息�Q�如下：
sendRPCDone(frameElement, "", new Array(), new Array(), new Array(""));
所以我们再前台接受到这个文本信息之后，应该写一个sendRPCDone的函数来做进一步信息处�?比如说列表出查询�l�果)�?br />
3) 前台文本处理代码�Q?br />


4。家庭作�?:)

一定要自己写一些代码，才能巩固知识:)
题目�Q?br />我们�l�常�?a >del.icio.us来收藏我们喜�Ƣ的�|�站或者文章，�q�加一些类��D��书笔记的注释。那么我们怎么利用del.icio.us提供的API来访问我们的��M��W�记信息�Q��ƈ昄��在自��q��Blog里呢�Q?br />提示�Q?br />1。你要有一个del.icio.us的�̎��P��q�且已经有所�|�页收藏作�ؓ实验数据:)
2。API URL �?"http://del.icio.us/feeds/json/" + "你的账号�?�Q�自己参看一下，看返回什么样的格式文本。另外，如果要限制返回的记录敎ͼ�可以�??count=10"�q�样的参数�?br />

最后，��大家中�U�愉快！

---------------------------�?---------------------------

Dedian 2006-10-07 07:05 发表评论


results go here . . .

PHP/Java Integration on Windows

Dedian — Fri, 06 Oct 2006 01:05:00 GMT
reference: http://us3.php.net/java
help doc: http://php-java-bridge.sourceforge.net/

1- Make sure u have Installed Apache 2 & PHP 5 and Java J2EE 1.5 2- download pecl-5.0.5-Win32.zip and php-java-bridge_2.0.8.zip, which will include extra dll(s)    - unpack pecl pkg to your extensions folder, in PHP5 its ext.    - unpack java-Bridge to root php folder, in my case its simply C:\PHP    Note: 1. the java-Bridge inculdes new versions of certain files like php_java.dll    so, it would be wise to rename your old files that came with PECL pkg for example    file_old, to rollback at anytime. 2. Don't run batch file under php-java-bridge after unpacking to php root folder, just add following lines in php.ini configure file (depends on installation fold of j2ee): extension=php_java.dll extension_dir = "C:\php\ext" [java] java.java_home=C:\Program Files\Java\jre1.5.0_06 java.java=C:\Program Files\Java\jre1.5.0_06\bin\javaw.exe java.log_level=2 ;java.log_file=ext/JavaBridge.log

Dedian 2006-10-06 09:05 发表评论

HttpURLConnect Problem

Dedian — Wed, 20 Sep 2006 22:32:00 GMT
When I try to get some information of http connection to some websites (say http://linuxbyte.net) by function HttpURLConnection.getResponseCode(), it seems tthat JVM hangs for quite a while. Somebody says that is maybe the problem of http server who must be a Microsoft webserver. Here and here are the bug report information for Java 1.3 or before. Though it is said that the problem has been solved after java 1.4, i still get undesirable a long time waiting before a SocketException (Connection reset) is thrown out. Btw, conn.setConnectTimeout or conn.setConnectTimeout is involved for this problem. I am not sure if there is any method that can save time to skip those bad links.

Dedian 2006-09-21 06:32 发表评论

Getting the IP Address and Hostname

Dedian — Thu, 17 Aug 2006 22:53:00 GMT

1. Getting the IP Address of a Hostname

try
{
InetAddress addr = InetAddress.getByName("yahoo.com");
byte[] ipAddr = addr.getAddress();

// Convert to dot representation
String ipAddrStr = "";
for (int i=0; i if (i > 0) {
ipAddrStr += ".";
}
ipAddrStr += ipAddr[i]&0xFF;
}
}
catch (UnknownHostException e) {
}

2. Getting the Hostname of an IP Address
This example attempts to retrieve the hostname for an IP address. Note that getHostName() may not succeed, in which case it simply returns the IP address.

try {
// Get hostname by textual representation of IP address
InetAddress addr = InetAddress.getByName("127.0.0.1");

// Get hostname by a byte array containing the IP address
byte[] ipAddr = new byte[]{127, 0, 0, 1};
addr = InetAddress.getByAddress(ipAddr);

// Get the host name
String hostname = addr.getHostName();

// Get canonical host name
String hostnameCanonical = addr.getCanonicalHostName();
} catch (UnknownHostException e) {
}

3. Getting the IP Address and Hostname of the Local Machine
try {
InetAddress addr = InetAddress.getLocalHost();

// Get IP Address
byte[] ipAddr = addr.getAddress();

// Get hostname
String hostname = addr.getHostName();
} catch (UnknownHostException e) {
}

Dedian 2006-08-18 06:53 发表评论

CVS Tutorial

Dedian — Wed, 19 Jul 2006 23:06:00 GMT

-- Getting Ready to Use CVS
First set the variable CVSROOT to /class/`username`/cvsroot
[Or any other directory you wish]
[For csh/tcsh: setenv CVSROOT ~/cvsroot]
[For bash/ksh: CVSROOT=~/cvsroot;export CVSROOT]

Next run cvsinit. It will create this directory along with the subdirectory CVSROOT and put several files into CVSROOT.

-- How to put a project under CVS
A simple program consisting of multiple files is in /workspaces/project.

To put this program under cvs first

cd to /workspaces/project

Next

cvs import -m "Sample Program" project sample start

CVS should respond with
N project/Makefile
N project/main.c
N project/bar.c
N project/foo.c

No conflicts created by this import

If your were importing your own program, you could now delete the original source.
(Of course, keeping a backup is always a good idea)

-- Basic CVS Usage
Now that you have added 'project' to your CVS repository, you will want to be able to modify the code.

To do this you want to check out the source. You will want to cd to your home directory before you do this.

cd

cvs checkout project

CVS should respond with
cvs checkout: Updating project
U project/Makefile
U project/bar.c
U project/foo.c
U project/main.c

This creates the project directory in your home directory and puts the files: Makefile, bar.c, foo.c, and main.c into the directory along with a CVS directory which stores some information about the files.

You can now make changes to any of the files in the source tree.
Lets say you add a printf("DONE\n"); after the function call to bar()
[Or just cp /class/bfennema/project_other/main2.c to main.c]

Now you have to check in the new copy

cvs commit -m "Added a DONE message." main.c

CVS should respond with
Checking in main.c;
/class/'username'/cvsroot/project/main.c,v <-- main.c
new revision: 1.2; previous revision: 1.1
done

Note, the -m option lets you define the checking message on the command line. If you omit it you will be placed into an editor where you can type in the checking message.

-- Using CVS with Multiple Developers
To simulate multiple developers, first create a directory for your second developer.
Call it devel2 (Create it in your home directory).
Next check out another copy of project.
HINT: cvs checkout project
Next, in the devel2/project directory, add a printf("YOU\n"); after the printf("BAR\n");
[Or copy /class/bfennema/project_other/bar2.c to bar.c]

Next, check in bar.c as developer two.
HINT: cvs commit -m "Added a YOU" bar.c
Now, go back to the original developer directory.
[Probably /class/'username'/project]

Now look at bar.c. As you can see, the change made by developer one has no been integrated into your version. For that to happen you must

cvs update bar.c

CVS should respond with
U bar.c

Now look at bar.c. It should now be the same as developer two's.
Next, edit foo.c as the original developer and add printf("YOU\n"); after the printf("FOO\n");
[Or copy /class/bfennema/project_other/foo2.c to foo.c]

Then check in foo.c

HINT: cvs commit -m "Added YOU" foo.c
Next, cd back to developer two's directory.
Add printf("TOO\n"); after the printf("FOO\n");
[Or copy /class/bfennema/project_other/foo3.c to foo.c]

Now type

cvs status foo.c

CVS should respond with
=================================================================== File: foo.c Status: Needs Merge Working revision: 1.1.1.1 'Some Date' Repository revision: 1.2 /class/'username'/cvsroot/project/foo.c,v Sticky Tag: (none) Sticky Date: (none) Sticky Options: (none)
The various status of a file are:
Up-to-date
The file is identical with the latest revision in the repository.
Locally Modified
You have edited the file, and not yet committed your changes.
Needing Patch
Someone else has committed a newer revision to the repository.
Needs Merge
Someone else has committed a newer revision to the repository, and you have also made modifications to the file.

Therefore, this is telling use we need to merge our changes with the changes made by developer one. To do this

cvs update foo.c

CVS should respond with
RCS file: /class/'username'/cvsroot/project/foo.c,v
retrieving revision 1.1.1.1
retrieving revision 1.2
Merging differences between 1.1.1.1 and 1.2 into foo.c
rcsmerge: warning: conflicts during merge
cvs update: conflicts found in foo.c
C foo.c

Since the changes we made to each version were so close together, we must manually adjust foo.c to look the way we want it to look. Looking at foo.c we see:
void foo() { printf("FOO\n"); <<<<<<< foo.c printf("TOO\n"); ======= printf("YOU\n"); >>>>>>> 1.2 }

We see that the text we added as developer one is between the ======= and the >>>>>>> 1.2.
The text we just added is between the ======= and the <<<<<<< foo.c

To fix this, move the printf("TOO\n");to after the printf("YOU\n");line and delete the additional lines the CVS inserted. [Or copy /class/bfennema/project_other/foo4.c to foo.c]
Next, commit foo.c

cvs commit -m "Added TOO" foo.c

Since you issued a cvs update command and integrated the changes made by developer one, the integrated changes are committed to the source tree.

-- Additional CVS Commands
To add a new file to a module:
Get a working copy of the module.
Create the new file inside your working copy.
use cvs add filename to tell CVS to version control the file.
use cvs commit filename to check in the file to the repository.

Removing files from a module:
Make sure you haven't made any uncommitted modifications to the file.
Remove the file from the working copy of the module. rm filename.
use cvs remove filename to tell CVS you want to delete the file.
use cvs commit filename to actually perform the removal from the repository.

For more information see the cvs man pages or the cvs.ps file in cvs-1.7/doc.

---------------
copy from http://www.csc.calpoly.edu/~dbutler/tutorials/winter96/cvs/

Dedian 2006-07-20 07:06 发表评论

Retrieve values in HashTable or HashMap

Dedian — Thu, 01 Jun 2006 23:16:00 GMT
Unlike collection types such as Vector or List, Map (HashTable or HashMap) accesses a value by a key. If we want to retrieve all the values that have been put in a Map, one of simple ways to do that is employing a Collection or plus an Iterator, here is the sample code (just retrieve vaules, skip keys), assuming there is a variable: HashMap> links

Collection c = links.value();
Vector v = new Vector(c);
for(int i = 0; i< v.size(); i++)
{
    ComplexDataType tempData = (ComplexDataType)v.get(i);
    dosomethingwith(tempData);
}

P.S. Map provides three views of map: keySet, entrySet and values collection, we can use any of them .

Dedian 2006-06-02 07:16 发表评论

Java Reading & Writing file

Dedian — Wed, 31 May 2006 00:12:00 GMT
1. Reading text from Standard Input

try
{
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
String str = "";
while (str != null)
{
System.out.print("> some prompt ");
str = in.readLine();
dosomethingwith(str);
}
}
catch (IOException e)
{
}

2. Reading text from a file

try
{
BufferedReader in = new BufferedReader(new FileReader("filename"));
String str;
while ((str = in.readLine()) != null)
{
dosomethingwith(str);
}
in.close();
}
catch (IOException e)
{
}

3. Reading a file into a BityArray

// Returns the contents of the file in a byte array.
public static byte[] getBytesFromFile(File file) throws IOException
{
InputStream is = new FileInputStream(file);

// Get the size of the file
long length = file.length();

// You cannot create an array using a long type.
// It needs to be an int type.
// Before converting to an int type, check
// to ensure that file is not larger than Integer.MAX_VALUE.
if (length > Integer.MAX_VALUE)
{
// File is too large
}

// Create the byte array to hold the data
byte[] bytes = new byte[(int)length];

// Read in the bytes
int offset = 0;
int numRead = 0;
while (offset < bytes.length
&& (numRead=is.read(bytes, offset, bytes.length-offset)) >= 0)
{
offset += numRead;
}

// Ensure all the bytes have been read in
if (offset < bytes.length)
{
throw new IOException("Could not completely read file "+file.getName());
}

// Close the input stream and return bytes
is.close();
return bytes;

}

4. Writing to a file

try
{
BufferedWriter out = new BufferedWriter(new FileWriter("filename"));
out.write("some string");
out.close();
}
catch (IOException e)
{
}
Note: If the file does not already exist, it is automatically created.

5. Appending to a file

try
{
BufferedWriter out = new BufferedWriter(new FileWriter("filename", true));
out.write("appending String");
out.close();
}
catch (IOException e)
{
}

6. Using a Random Access File

try
{
File f = new File("filename");
RandomAccessFile raf = new RandomAccessFile(f, "rw");

// Read a character
char ch = raf.readChar();

// Seek to end of file
raf.seek(f.length());

// Append to the end
raf.writeChars("aString");
raf.close();
}
catch (IOException e)
{
}

reference:
http://javaalmanac.com/egs/java.io/pkg.html

Dedian 2006-05-31 08:12 发表评论

convertion between InputStream & String

Dedian — Fri, 28 Apr 2006 21:17:00 GMT
1. String --> InputStream

InputStream convertToInputStream(String str)
{
        ByteArrayInputStream is = new ByteArrayInputStream(str.getBytes());
        return is;
}

2. InputStream --> String

String convertToString(InputStream is)
{

       BufferedReader in = new BufferedReader(new InputStreamReader(is));
        StringBuffer buffer = new StringBuffer();
        String line = "";
        while ((line = in.readLine()) != null)
        {
             buffer.append(line);
         }
         return buffer.toString();

}

When I do the socket programming, I always need to deal with inputstream and string, above are the basic ways to so that, but I am not sure if there are any simpler ways to do that...

Dedian 2006-04-29 05:17 发表评论

Simple way to convert between int & String in Java

Dedian — Tue, 25 Apr 2006 01:22:00 GMT
It is common problem of convertion between int & string for certian computer language. Well, in Java, following are some easy ways I usually apply:

1. int --> String
    a. apply "+" operation with an empty string
          ex:
          int index = 20;
          String indexStr = "" + index;
    b. use String function
          ex:
          int index = 20;
          String indexStr = String.valueOf(index);
    c. convert to Integer class firstly
          ex:
          int index = 20;
          Integer Index = new Integer(index);
          String indexStr = Index.toString();
          or
          String indexStr = Integer.toString(index);

2. String --> int
    a. use class Integer parse funtion
       ex:
       String indexStr = "20";
       int index = Integer.parseInt(indexStr);
       or
       int index = (new Integer(indexStr)).intValue();

note: above convertion methods can be applied to other number types, such as float, long, double...

P.S. for 1.a method, should be noticed that following two expression are different:
int i = 7;
int j = 8;

String str1 = i + j + ""; //(str1 == "15")
String str2 = "" + i + j; //(str2 == "78")

Dedian 2006-04-25 09:22 发表评论

亚洲国产精品自在拍在线播放,18禁亚洲深夜福利人口,中文字幕专区在线亚洲

Again, Problem or Bug for URLConnection ?

Ajax ���谈

PHP/Java Integration on Windows

HttpURLConnect Problem

Getting the IP Address and Hostname

1. Getting the IP Address of a Hostname

2. Getting the Hostname of an IP Address

3. Getting the IP Address and Hostname of the Local Machine

CVS Tutorial

-- Getting Ready to Use CVS

-- How to put a project under CVS

-- Basic CVS Usage

-- Using CVS with Multiple Developers

-- Additional CVS Commands

Retrieve values in HashTable or HashMap

Java Reading & Writing file

convertion between InputStream & String

Simple way to convert between int & String in Java

Ajax ��谈