Category: Java

Just found Objectify on http://code.google.com/p/objectify-appengine/

The Google App Engine/J low-level datastore API is simple and elegant, neatly reducing your data operations to four simple methods: get, put, delete, and query. However, it is not designed to be used by the average developer:

DatastoreService persists GAE-specific Entity objects rather than normal POJO classes.
DatastoreService Keys are untyped and error-prone.
DatastoreService has a machine-friendly but not human-friendly query interface.
DatastoreService has an unnecessarily complicated transaction API.
DatastoreService is rather poorly documented. You get to figure it all out from the Javadocs.

I have made a simple Java BBCode Implementation, and it is open source and free to use. Feel free to take it into your project.

Below is the Java static method to convert the bbcode-based text into HTML form to be displayed in browser.

public static String bbcode(String text) {

String temp = nl2br(text);

Map<string , String> bbMap = new HashMap</string><string , String>();</string>

bbMap.put(“\\[b\\](.+?)\\[/b\\]”, “<strong>$1</strong>”);

bbMap.put(“\\[i\\](.+?)\\[/i\\]”, “<span style=’font-style:italic;’>$1</span>”);

bbMap.put(“\\[u\\](.+?)\\[/u\\]”, “<span style=’text-decoration:underline;’>$1</span>”);

bbMap.put(“\\[h1\\](.+?)\\[/h1\\]”, “<h1>$1</h1>”);

bbMap.put(“\\[h2\\](.+?)\\[/h2\\]”, “<h2>$1</h2>”);

bbMap.put(“\\[h3\\](.+?)\\[/h3\\]”, “<h3>$1</h3>”);

bbMap.put(“\\[h4\\](.+?)\\[/h4\\]”, “<h4>$1</h4>”);

bbMap.put(“\\[h5\\](.+?)\\[/h5\\]”, “<h5>$1</h5>”);

bbMap.put(“\\[h6\\](.+?)\\[/h6\\]”, “<h6>$1</h6>”);

bbMap.put(“\\[quote\\](.+?)\\[/quote\\]”, “<blockquote>$1</blockquote>”);

bbMap.put(“\\[p\\](.+?)\\[/p\\]”, “<p>$1</p>”);

bbMap.put(“\\[p=(.+?),(.+?)\\](.+?)\\[/p\\]”, “<p style=’text-indent:$1px;line-height:$2%;’>$3</p>”);

bbMap.put(“\\[center\\](.+?)\\[/center\\]”, “<div align=’center’>$1”);

bbMap.put(“\\[align=(.+?)\\](.+?)\\[/align\\]”, “<div align=’$1′>$2”);

bbMap.put(“\\[color=(.+?)\\](.+?)\\[/color\\]”, “<span style=’color:$1;’>$2</span>”);

bbMap.put(“\\[size=(.+?)\\](.+?)\\[/size\\]”, “<span style=’font-size:$1;’>$2</span>”);

bbMap.put(“\\[img\\](.+?)\\[/img\\]”, “<img src=’$1′ />”);

bbMap.put(“\\[img=(.+?),(.+?)\\](.+?)\\[/img\\]”, “<img width=’$1′ height=’$2′ src=’$3′ />”);

bbMap.put(“\\[email\\](.+?)\\[/email\\]”, “<a href=’mailto:$1′>$1</a>”);

bbMap.put(“\\[email=(.+?)\\](.+?)\\[/email\\]”, “<a href=’mailto:$1′>$2</a>”);

bbMap.put(“\\[url\\](.+?)\\[/url\\]”, “<a href=’$1′>$1</a>”);

bbMap.put(“\\[url=(.+?)\\](.+?)\\[/url\\]”, “<a href=’$1′>$2</a>”);

bbMap.put(“\\[video\\](.+?)\\[/video\\]”, “<video src=’$1′ />”);

for (Map.Entry entry: bbMap.entrySet()) {

temp = temp.replaceAll(entry.getKey().toString(), entry.getValue().toString());

}

return temp;

}

---

6 June 2011
Refer to stackoverflow, there is one topic that is related to Java BBCode I discovered just now.

This is a simple article that how to hello world to DWR (Direct Web Remoting).

First, go http://directwebremoting.org/dwr/download.html download dwr.jar, for me I download 2.0.6 version in order it can be supported in Google Appengine. Put dwr.jar in WEB-INF/lib

Second, download commons-logging-1.1.1.jar, put this jar in WEB-INF/lib also.

Third, modify web.xml to add this content of

    <servlet>
  <servlet-name>dwr-invoker</servlet-name>
  <display-name>DWR Servlet</display-name>
  <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
  <init-param>
     <param-name>debug</param-name>
     <param-value>true</param-value>
  </init-param>
</servlet>

<servlet-mapping>
  <servlet-name>dwr-invoker</servlet-name>
  <url-pattern>/dwr/*</url-pattern>
</servlet-mapping>

Fourth, create dwr.xml and with the content of

<!DOCTYPE dwr PUBLIC
    "-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN"
    "http://getahead.org/dwr/dwr20.dtd">

<dwr>
  <allow>
    <create creator="new" javascript="DWRStuff">
      <param name="class" value="com.fyhao.secs.DWRStuff"/>
    </create>
  </allow>
</dwr>

Then you have to create DWRStuff.java file with the content of

package com.fyhao.secs;

public class DWRStuff {

    public String shownum(int a) {
        return "" + (a * 3);
    }
}

Create a JSP file, called ajax.jsp with the content of

<%@ page contentType="text/html; charset=utf-8" language="java" import="java.sql.*" errorPage="" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<script src=’dwr/interface/DWRStuff.js’></script>
<script src=’dwr/engine.js’></script>
<script type="text/javascript">
function update() {
    DWRStuff.shownum(5, function(data) {
                                 alert(data);
                                 });
}
</script>
</head>

<body>
<div id="num"></div>
<script>update();
</script>
</body>
</html>

Remember the DWRStuff.js shown in the script source there.

Now, you can try to see if it is success.

There is sometime coding JPA persist data problem may occured.

For example, I have a code that is about:

public class MemberBean {

    public void registerMember(Members member) {
        EntityManager em = EMF.get().createEntityManager();
        try {
            em.persist(member);
            //em.refresh(member);
        } finally {
            em.close();
        }
    }

As you can see that, if you run this code, sometimes you will got:

Problem accessing /fyhaosecs. Reason:

    Illegal argument

Caused by:

javax.persistence.PersistenceException: Illegal argument
	at org.datanucleus.jpa.NucleusJPAHelper.getJPAExceptionForJDOException(NucleusJPAHelper.java:214)
	at org.datanucleus.jpa.EntityManagerImpl.close(EntityManagerImpl.java:157)
	at org.datanucleus.store.appengine.jpa.DatastoreEntityManager.close(DatastoreEntityManager.java:54)
	at com.fyhao.secs.MemberBean.registerMember(MemberBean.java:18)
	at com.fyhao.secs.FyhaosecsServlet.doGet(FyhaosecsServlet.java:24)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:693)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)

Solution:

The solution is: just add em.refresh(member); after you persist.

You can also refer to this link: http://www.datanucleus.org/products/accessplatform_1_1/jpa/em.html

Discuz! is a forum software developed by Comsenz. authcode is a function that able to encrypt the string into human unreadable form and also can decrypt it. The beauty inside is how many times you make encryption, the encrypted string is not same at all, but when you make decryption it is able to change back to original string. Comsenz had made great contribution to the PHP world by authcode function, whereas nowadays many of the PHP developers are using authcode function in their project, even me.

Now, I would like to find some way using Java to manipulate authcode function. However my skill is not talentable from getting authcode function works. Therefore, I searched online and found that the post rain.xie posted on Javaeye Forum. I changed a little bit from there to be hosted on Google Appengine along with my project. Notice that the implementation of Base64 Decoder I am using Google Appengine Library API.

Here is the code:

AuthCode.java

package com.fyhao.gift.helper;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Calendar;
import java.util.Random;
import com.google.appengine.repackaged.com.google.common.util.Base64;

public class AuthCode {

    public enum DiscuzAuthcodeMode {
        Encode, Decode
    };

    public static String CutString(String str, int startIndex, int length) {
        if (startIndex >= 0) {
            if (length < 0) {
                length = length * -1;
                if (startIndex – length < 0) {
                    length = startIndex;
                    startIndex = 0;
                } else {
                    startIndex = startIndex – length;
                }
            }

            if (startIndex > str.length()) {
                return "";
            }

        } else {
            if (length < 0) {
                return "";
            } else {
                if (length + startIndex > 0) {
                    length = length + startIndex;
                    startIndex = 0;
                } else {
                    return "";
                }
            }
        }

        if (str.length() – startIndex < length) {

            length = str.length() – startIndex;
        }

        return str.substring(startIndex, startIndex + length);
    }

    public static String CutString(String str, int startIndex) {
        return CutString(str, startIndex, str.length());
    }

    public static String MD5(String pass) {
        byte[] defaultBytes = pass.getBytes();
        try{
             MessageDigest algorithm = MessageDigest.getInstance("MD5");
             algorithm.reset();
             algorithm.update(defaultBytes);
             byte messageDigest[] = algorithm.digest();

             StringBuffer hexString = new StringBuffer();
             for (int i=0;i<messageDigest.length;i++) {
            String hex = Integer.toHexString(0xFF & messageDigest[i]);
            if(hex.length()==1)
            hexString.append(‘0’);

            hexString.append(hex);
             }
             return hexString.toString();
        }
        catch(NoSuchAlgorithmException nsae){
        }

        return "";
    }

    public static boolean StrIsNullOrEmpty(String str) {
        //#if NET1
        if (str == null || str.trim().equals("")) {
            return true;
        }

        return false;
    }

    static private byte[] GetKey(byte[] pass, int kLen) {
        byte[] mBox = new byte[kLen];

        for (int i = 0; i < kLen; i++) {
            mBox[i] = (byte) i;
        }

        int j = 0;
        for (int i = 0; i < kLen; i++) {

            j = (j + (int) ((mBox[i] + 256) % 256) + pass[i % pass.length])
                    % kLen;

            byte temp = mBox[i];
            mBox[i] = mBox[j];
            mBox[j] = temp;
        }

        return mBox;
    }

    public static String RandomString(int lens) {
        char[] CharArray = { ‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘j’, ‘k’,
                ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’,
                ‘x’, ‘y’, ‘z’, ‘0’, ‘1’, ‘2’, ‘3’, ‘4’, ‘5’, ‘6’, ‘7’, ‘8’, ‘9’ };
        int clens = CharArray.length;
        String sCode = "";
        Random random = new Random();
        for (int i = 0; i < lens; i++) {
            sCode += CharArray[Math.abs(random.nextInt(clens))];
        }
        return sCode;
    }

    public static String authcodeEncode(String source, String key, int expiry) {
        return authcode(source, key, DiscuzAuthcodeMode.Encode, expiry);

    }

    public static String authcodeEncode(String source, String key) {
        return authcode(source, key, DiscuzAuthcodeMode.Encode, 0);

    }

    public static String authcodeDecode(String source, String key) {
        return authcode(source, key, DiscuzAuthcodeMode.Decode, 0);

    }

    private static String authcode(String source, String key,
            DiscuzAuthcodeMode operation, int expiry) {
        try {
            if (source == null || key == null) {
                return "";
            }

            int ckey_length = 4;
            String keya, keyb, keyc, cryptkey, result;

            key = MD5(key);

            keya = MD5(CutString(key, 0, 16));

            keyb = MD5(CutString(key, 16, 16));

            keyc = ckey_length > 0 ? (operation == DiscuzAuthcodeMode.Decode ? CutString(
                    source, 0, ckey_length)
                    : RandomString(ckey_length))
                    : "";

            cryptkey = keya + MD5(keya + keyc);

            if (operation == DiscuzAuthcodeMode.Decode) {
                byte[] temp;
                temp = Base64.decode(CutString(source, ckey_length));
                result = new String(RC4(temp, cryptkey));
                if (CutString(result, 10, 16).equals(CutString(MD5(CutString(result, 26) + keyb), 0, 16))) {
                    return CutString(result, 26);
                } else {
                    temp = Base64.decode(CutString(source+"=", ckey_length));
                    result = new String(RC4(temp, cryptkey));
                    if (CutString(result, 10, 16).equals(CutString(MD5(CutString(result, 26) + keyb), 0, 16))) {
                        return CutString(result, 26);
                    } else {
                        temp = Base64.decode(CutString(source+"==", ckey_length));
                        result = new String(RC4(temp, cryptkey));
                        if (CutString(result, 10, 16).equals(CutString(MD5(CutString(result, 26) + keyb), 0, 16))) {
                            return CutString(result, 26);
                        }else{
                            return "2";
                        }
                    }
                }
            } else {
                source = "0000000000" + CutString(MD5(source + keyb), 0, 16)
                        + source;

                byte[] temp = RC4(source.getBytes("GBK"), cryptkey);

                return keyc + Base64.encode(temp);

            }
        } catch (Exception e) {
            return "";
        }

    }

    private static byte[] RC4(byte[] input, String pass) {
        if (input == null || pass == null)
            return null;

        byte[] output = new byte[input.length];
        byte[] mBox = GetKey(pass.getBytes(), 256);

        int i = 0;
        int j = 0;

        for (int offset = 0; offset < input.length; offset++) {
            i = (i + 1) % mBox.length;
            j = (j + (int) ((mBox[i] + 256) % 256)) % mBox.length;

            byte temp = mBox[i];
            mBox[i] = mBox[j];
            mBox[j] = temp;
            byte a = input[offset];

            byte b = mBox[(toInt(mBox[i]) + toInt(mBox[j])) % mBox.length];

            output[offset] = (byte) ((int) a ^ (int) toInt(b));
        }

        return output;
    }

    public static int toInt(byte b) {
        return (int) ((b + 256) % 256);
    }

    public long getUnixTimestamp() {
        Calendar cal = Calendar.getInstance();
        return cal.getTimeInMillis() / 1000;
    }

}