J2EE Developer & Photography enthusiast
I’ve just released a small update to JTexFileParser adding the ability to export text file data to XML.
Check it out at google code.
JTexFileParser is a java package built for simplifing delimited text files parsing. It gives you a quick way for parsing a delimited text file, managing rows and row’s fields.
I know that mixing scriplets and JSTL in JSP is a bad practice, but sometimes you can’t avoid it and every time I do it I can’t remember how to share variables between scriplets and JSTL so this post is a sort of reminder for the future. Hope it can be useful for other forgetful persons like me :-)
<% String myVariable = "Test"; pageContext.setAttribute("myVariable", myVariable); %>
<c:out value="myVariable"/><c:set var="myVariable" value="Test"/><% String myVariable = (String)pageContext.getAttribute("myVariable"); out.print(myVariable); %>
A well written article on JavaWorld that explains how to effectively use the Runtime.exec() method. It really saved me a lot of time.
This simple method shows hot to write to text files using Java.
If the file exists it will append the new text to it, otherwise it creates a new file. This is achieved using the FileWriter class and its constructor:
public FileWriter(String fileName, boolean append) throws IOException
Constructs a FileWriter object given a file name with a boolean indicating whether or not to append the data written. JavaDoc.
public void writeToFile(String text, String filePath){ try { File thisFile = new File(filePath); BufferedWriter writer = new BufferedWriter( new FileWriter(filePath, thisFile.exists())); writer.write( text ); writer.newLine(); writer.flush(); writer.close(); } catch (IOException e) { e.printStackTrace(); } }
A java implementation of the Unix tail command. This is a small customization of the java tail class created by Luigi Viggiano. I’ve just added some controls and added the update time parameter.
import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; /** * Java implementation of the Unix tail command * * @param args[0] File name * @param args[1] Update time (seconds). Optional. Default value is 1 second * * @author Luigi Viggiano (original author) http://it.newinstance.it/2005/11/19/listening-changes-on-a-text-file-unix-tail-implementation-with-java/ * @author Alessandro Melandri (modified by) * */ public class Tail { static long sleepTime = 1000; public static void main(String[] args) throws IOException { if (args.length > 0){ if (args.length > 1) sleepTime = Long.parseLong(args[1]) * 1000; BufferedReader input = new BufferedReader(new FileReader(args[0])); String currentLine = null; while (true) { if ((currentLine = input.readLine()) != null) { System.out.println(currentLine); continue; } try { Thread.sleep(sleepTime); } catch (InterruptedException e) { Thread.currentThread().interrupt(); break; } } input.close(); } else { System.out.println("Missing parameter!\nUsage: java JavaTail fileName [updateTime (Seconds. default to 1 second)]"); } } }
I’ve tested this procedure on Fedora 10 and Ubuntu 9.04 but It should work on other distributions too.
First of all download the latest JDK package from the SUN page: be sure to download the bin file and not the rpm.
From now on you’ll need to run commands using ”sudo”.
Move the package to /opt/ and make it executable.
cd /path/to/download/folder mv jdk-versionnumber-linux-i586.bin /opt/ cd /opt/ chmod +x jdk-versionnumber-linux-i586.bin
Now start the installation and follow the onscreen instructions
./jdk-versionnumber-linux-i586.binWhen the installation is done you’ll need to set the JAVA_HOME enviroment variable and add java executable to the system pah.
Open the file /etc/profile and add the following lines
JAVA_HOME="/opt/jdk_versionnumber" export JAVA_HOME PATH=$PATH:/opt/jdk_versionnumber/bin/ export PATH
Now add a symbolic link for the java command
ln -s /opt/jdk_versionnumber/bin/java /usr/bin/java
Log off and log in back and you’re done.
This is a simple example on how to get the WEB-INF directory path in a J2EE web application.
public class MyClassName{ private static final String WEBINF = "WEB-INF"; public String getWebInfPath(){ String filePath = ""; URL url = MyClassName.class.getResource("MyClassName.class"); String className = url.getFile(); filePath = className.substring(0,className.indexOf(WEBINF) + WEBINF.length()); return filePath; } }
This is a simple class that I usually use to connect to a MySQL database. Obviously the right MySQL JDBC driver must be in your classpath.
import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; public class ConnectionManager { // Connection data -- START static final String driver = "com.mysql.jdbc.my_driver_version"; static final String dbserver = "mysql.server.name"; static final String dbport = "mysql.database.port"; static final String dbname = "mysql.database.name"; static final String dbuser = "mysql.database.username"; static final String dbpass = "mysql.database.password"; // Connection data -- END /** * Opens a connection to the database * * @return Returns a Connection object */ public static Connection getConnection(){ Connection con = null; try { Class.forName(driver).newInstance(); String conString = "jdbc:mysql://"+dbserver+":"+dbport+"/"+dbname; con = DriverManager.getConnection(conString,dbuser, dbpass); } catch (InstantiationException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } return con; } public static void close(Object object){ if (object != null){ try { if (object instanceof Connection) ((Connection)object).close(); else if (object instanceof Statement) ((Statement)object).close(); else if (object instanceof PreparedStatement) ((PreparedStatement)object).close(); else if (object instanceof ResultSet) ((ResultSet)object).close(); } catch (SQLException e) { e.printStackTrace(); } finally { object = null; } } } }