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 
Access scriptlet variable with JSTL
<%
String myVariable = "Test";
pageContext.setAttribute("myVariable", myVariable);
%><c:out value="myVariable"/>
Access JSTL variable with scriptlet
<c:set var="myVariable" value="Test"/>
<%
String myVariable = (String)pageContext.getAttribute("myVariable");
out.print(myVariable);
%>
Tags: Java, JSP, JSTL, scriptlet, sharing, variables -
A well written article on JavaWorld that explains how to effectively use the Runtime.exec() method. It really saved me a lot of time.
When Runtime.exec() won’t – JavaWorld
Tags: Java, link -
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();
}
}
Tags: file, FileWriter, Java, Text -
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)]");
}
}
}
Tags: Java -
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.bin
When 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.
Tags: Java, JDK, Linux -
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;
}
}
Tags: J2EE, Java -
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;
}
}
}
}
Tags: Java, JDBC, MySQL -
