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Thursday, October 20, 2011

Linux : chmod: WARNING: chmod: could not getcwd OR chown: getcwd: Permission denied

When I tried to do chmod for a bulk of files at once using below mentioned chmod command, I used to get below error.
Below command is used for changing permission for a bulk of files recursively in a single shot.

Command : chmod -R 777 *

Error :

chmod: WARNING: chmod: could not getcwd /home/test

Also when i tried to do chown for a bulk of files at once using below mentioned chown command, I used to get error as shown below.
Below command is used to change owner name for a bulk of files recursively in a single shot.

Command : chown -R UserName:GroupName *

Error :

chown: getcwd: Permission denied

However when I do chmod or chown for one particular folder, it runs without error.

Command : chmod -R 777 FolderName
Command : chown -R UserName:GroupName FolderName

Reason :
On some Unix variants, getcwd() will return FALSE if any one of the parent directories does not have the readable or search mode set, even if the current directory does.

Solution :
Type "groups" command and see which other groups you can access.
Go to the parent folder and change the group name.
And then try the above commands, It worked for me and hope it may even work for you.

If not lets discuss it here.

Tuesday, October 18, 2011

Simple HTML parser in Java

Some time we may require to parse a HTML file. In this example i used jsoup: Java HTML Parser because its simple to configure and easy to understand with lots of feature which can be customize according to our requirement. http://jsoup.org/
We used the jsoup jar (version 1.6.1), To run this example download jsoup-1.6.1.jar and set it in your classpath.

We can either hit a HTTP URL or read from a HTML file according to our requirement.

The parse(File in, String charsetName) method loads and parses a HTML file.
File input = new File("/tmp/input.html");
Document doc = Jsoup.parse(input,"UTF-8");

The connect(String url) method creates a new Connection, and get() fetches and parses a HTML file.
Document doc = Jsoup.connect("http://example.com/").get();

Also you can parse a document from a String
String html = "<html><head><title>First parse</title></head>"
+ "<body><p>Parsed HTML into a doc.</p></body></html>";
Document doc = Jsoup.parse(html);

Lets look at API for jsoup. http://jsoup.org/apidocs/

Lets see a sample code, you can customize it according to your requirement. Just set jsoup-1.6.1.jar in your classpath, provide a HTMl file to read and run the program.

/* SimpleHTMLParser.java */

import java.io.File;
import java.io.IOException;
import java.util.Iterator;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Attribute;
import org.jsoup.nodes.Attributes;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

public class SimpleHTMLParser {

    public static void main(String[] args) throws IOException {


        //File htmlFile = new File("C:/temp/VariableDeclarations.html");
        //Document doc = Jsoup.parse(htmlFile, "UTF-8");

        Document doc = Jsoup.connect("http://localhost:8080/temp/VariableDeclarations.html").get();

        Element headElement = doc.head();//Accessor to the document's head element.
        Elements allHeadElements = headElement.children();//Get this element's child elements.

        //For formatting output
        String indent = "";

        parseElements(allHeadElements,indent);

        Element bodyElement = doc.body();//Accessor to the document's body element.
        Elements allBodyElements = bodyElement.children();//Get this element's child elements.

        parseElements(allBodyElements,indent);

    }

    public static void parseElements(Elements allElements,String indent) {

        //For formatting output
        indent += " ";

        if(!allElements.isEmpty()) {

                for(int i=0;i<allElements.size();i++) {

                Element eachChildrenElement = allElements.get(i);

                //If the tag has text values
                if(eachChildrenElement.hasText()) {

                    Elements allChlidElements = eachChildrenElement.children();

                    //If Elements has child nodes, then call parseElements() recursively
                    if(allChlidElements.size() > 0) {
                        System.out.println(indent+eachChildrenElement.tagName());
                        parseElements(allChlidElements,indent);
                    }
                    //Else this is a leaf node, print the values
                    else {
                        System.out.println(indent+eachChildrenElement.tagName()+" : "+eachChildrenElement.text());
                    }
                }
                //Else check for attributes
                else {
                    Attributes attrs = eachChildrenElement.attributes();

                    Iterator<Attribute> itAttrs = attrs.iterator();

                    System.out.print(indent+eachChildrenElement.tagName()+" : Attributes :: ");

                    while(itAttrs.hasNext()) {
                        Attribute attr = itAttrs.next();
                        System.out.print(attr.getKey()+" - "+attr.getValue()+", ");
                    }
                    //For formatting output
                    System.out.println("");
                }
            }//for

        }
    }//parseElements

}

Thursday, October 13, 2011

Exception in thread "main" java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: YES)

if you get below mentioned exceptions while connecting My SQL using JDBC, Just make sure that password and other login credentials are provided correctly.

Exception in thread "main" java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: YES)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1056)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:957)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3376)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3308)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:894)
        at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:3808)
        at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1256)
        at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2032)
        at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:729)
        at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:46)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
        at java.lang.reflect.Constructor.newInstance(Unknown Source)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
        at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:302)
        at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:283)
        at java.sql.DriverManager.getConnection(Unknown Source)
        at java.sql.DriverManager.getConnection(Unknown Source)

Solution :

Just make sure that password you provide is correct, Cross check the password you have provided.

Below is the simple JDBC test program, To run this program make sure you add Jar file like mysql-connector-java-5.1.5.jar to classpath.

Make sure you provide all correct login credentials in Step 2. i.e. port, database name and password.

/* Test.java */

import java.sql.*;
public class Test
{
public static void main(String[] args) throws Exception
{
Connection con;
Statement stat;
Class.forName("com.mysql.jdbc.Driver");//Step 1: Loading Drivers

con=DriverManager.getConnection("jdbc:mysql://localhost:3306/Test","root","password");//Step 2: Making Connection

stat=con.createStatement();//Step 3: Creating JDBC Statement

String query = "select * from table_name;";

ResultSet rset=stat.executeQuery(query);//Step 4: Execute the Ststement

while(rset.next())//Step 5: Looping through the ResultSet
{
System.out.println(rset.getString(1));
}
stat.close();//step 6: Close the Connection and Statement
con.close();
}
}

Friday, October 7, 2011

org.apache.lucene.store.LockObtainFailedException

While creating index files for Lucene 3.0.2 search engine I got below mentioned error.

Exception:

org.apache.lucene.store.LockObtainFailedException: Lock obtain timed out: NativeFSLock@/export/home/Lucene/indexFiles/write.lock
        at org.apache.lucene.store.Lock.obtain(Lock.java:84)
        at org.apache.lucene.index.IndexWriter.init(IndexWriter.java:1060)
        at org.apache.lucene.index.IndexWriter.(IndexWriter.java:882)

Solution :

Check for IndexWriter object. Make sure you close IndexWriter object after completing index creation.
Check for any exceptions and close IndexWriter object if exception occurs.

Possible reason is there may be any exception occurred and you missed to close the IndexWriter object in catch block.

code snippte:

// Store the index in file
Directory directory = new SimpleFSDirectory(new File(indexLoc));
IndexWriter iwriter = new IndexWriter(directory, analyzer, isNew,MaxFieldLength.UNLIMITED);

iwriter.optimize();
iwriter.close();

If you need complete tested code for Lucene 3.0.2 example, click here

Saturday, October 1, 2011

Java : File copy program

Simple Java program to copy a file from its source to destination. Simply provide source file and a destination directory in the below function copyFunction(File srcFile,File destDirectory).

/* FileCopyProgram.java */
import java.io.*;
public class FileCopyProgram
{
public void copyFunction(File srcFile,File destDirectory)
{
try
{
String srcFilePath = srcFile.getPath();
String fileName = srcFilePath.substring(srcFilePath.lastIndexOf("\\")+1);
File destFile = new File(destDirectory.getPath()+"\\"+fileName);
InputStream inSrc = new FileInputStream(srcFile);
OutputStream outDest = new FileOutputStream(destFile);
byte[] buffer = new byte[4096];
int bytesRead;
while ((bytesRead = inSrc.read(buffer)) > 0)
{
outDest.write(buffer, 0, bytesRead);
}
inSrc.close();
outDest.close();
System.out.println("File copy sucessfully : "+fileName);
}
catch (IOException ex)
{
System.out.println("Exception in copy : "+ex);
}
}
public static void main(String[] args)
{
FileCopyProgram cf = new FileCopyProgram();
cf.copyFunction(new File("C:\\Test\\Noname1.txt"),new File("D:\\Software"));
}
}

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