tag ‍“java”

sql IN logical operation for java

by Hamid Reza Fahimi Madjd @ Apr 20, 2009

Hi,
have you ever needed sql IN for java language ?
OK, in this post I'm going to use new java 5 feature (varargs method) to simulate sql IN:

public static boolean in(int i, int... ints) {
Arrays.sort(ints);
return Arrays.binarySearch(ints, i) >= 0;
}

as you see, our function gets 2 parameters, first one is your desired value and second one is your search list.
now, when you call the method:

public static void main(String[] args) {
System.out.println(in(1, 2, 3, 4, 5, 1));
}

it returns:

true

i hope you find this tip useful;

java no comment

how to deploy war file into web root ?

by Hamid Reza Fahimi Madjd @ May 7, 2008

Some times we need deploy our peoject into root directory of your domain (not sub directory), to solve the problem:

1. make war file (for example myproject.war)
2. rename the war file to ROOT.war (attention the filename must be uppercase)
3. deploy war file

now, you can see / in tomcat web application manager page that deployed in site root.

java no comment

Set JFreeChart data from database

by Hamid Reza Fahimi Madjd @ Jan 15, 2008

A couple of days ago I needed to generate some charts using Java so I searched for a library which could do it. Soon I found JFreeChart library and downloaded it from here. But I was surprised when I saw the user guide wasn't free! Therefore I decided to write this post and describe how to obtain JFreeChart data from database (I'll use mysql database).

At first I copied jcommon-1.0.12.jar, jfreechart-1.0.9.jar and mysql-connector-java-5.0.7-bin.jar files to /WEB-INF/lib directory then I created a table in the database and filled it with below data:

type             count
----------------------
invoice_detail    3273
----------------------
object_status     2819
----------------------
service_sales_... 1540
----------------------
call_function     1183
----------------------
contact           904
----------------------
invoice           775
----------------------
payment           596

Now I create DatabaseChart servlet for connecting to database and generating my chart

import org.jfree.data.jdbc.JDBCPieDataset;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartUtilities;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import java.io.IOException;
import java.io.OutputStream;
import java.sql.SQLException;
import java.sql.DriverManager;
import java.sql.Connection;

public class DatabaseChart extends HttpServlet {

  public void doPost(HttpServletRequest request, response) throws ServletException, IOException {}

  public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    Connection connection = null;
    try {
      Class.forName("com.mysql.jdbc.Driver").newInstance();
      try {
        connection = DriverManager.getConnection("jdbc:mysql://localhost/my_db?user=my_un&password=my_pass&useUnicode=true&characterEncoding=utf-8");
      } catch (SQLException e) {
        e.printStackTrace();
      }
    } 
    catch (InstantiationException e) {
      e.printStackTrace();
    } 
    catch (IllegalAccessException e) {
      e.printStackTrace();
    } 
    catch (ClassNotFoundException e) {
      e.printStackTrace();
    }

    JDBCPieDataset dataset = new JDBCPieDataset(connection);
    try {
      dataset.executeQuery("Select `type`, `count` From my_table order by count desc");
      JFreeChart chart = ChartFactory.createPieChart("Pie Chart", dataset, true, true, false);
      if (chart != null) {
        response.setContentType("image/png");
        OutputStream out = response.getOutputStream();
        ChartUtilities.writeChartAsPNG(out, chart, 450, 400);
      }
    } 
    catch (SQLException e) {
      e.printStackTrace();
    }
    try {
      if(connection != null){connection.close();} 
    }
    catch (SQLException e) {e.printStackTrace();}
  }

}

at the end I add the servlet information to web.xml file

<servlet>
<servlet-name>generate_chart</servlet-name>
<servlet-class>DatabaseChart</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>generate_chart</servlet-name>
<url-pattern>/generate_chart</url-pattern>
</servlet-mapping>

now if you run the project you will get a chart like this

java, jfreechart no comment

How to search and sort primitive arrays in Java ?

by Hamid Reza Fahimi Madjd @ Jan 8, 2008

Always I was keen on solution for sorting and searching primitive arrays. Today I found java.util.Arrays class that includes some useful static methods for sorting, searching, filling and ... For sorting you can use Arrays.sort(aPrimitiveArray) static method, look here :

String[] test = {"d", "z", "a"};
Arrays.sort(test);
System.out.println(Arrays.toString(test));

The result will be:

[a, d, z]

As you see we've used Arrays.toString(test) for printing sorted array.

And for searching you can use Arrays.binarySearch(aPrimitiveArray, key) static method:

Arrays.sort(test);
System.out.println(Arrays.toString(test));
System.out.println(Arrays.binarySearch(test, "a"));

The result will be:

[a, d, z]
1

1 is index of found key otherwise it will be a less than zero number.

Attention: that before using Arrays.binarySearch(aPrimitiveArray, key) method you have to sort array by Arrays.sort(aPrimitiveArray) method.

array, java no comment

deploy war file without lib in Tomcat

by Hamid Reza Fahimi Madjd @ Dec 12, 2007

At this post I'd talk about how to decrease size of big war files and make deployment faster.
I have a 15 MB war file and the size of lib (jar files) directory is 14.8 MB! So I need a solution that enables me to upload my project lib directory just for once and after that deploy my war file without lib directory.

At first I renamed my lib directory to myprojlib and then copied (for example using ftp) it to ${tomcat home}/common/lib folder on the server.
After that I modify catalina.properties file in ${tomcat home}/conf and add my myprojlib path to common.loader according below:

common.loader=${catalina.home}/common/classes,
${catalina.home}/common/i18n/*.jar,
${catalina.home}/common/endorsed/*.jar,
${catalina.home}/common/lib/*.jar,
${catalina.home}/common/lib/myprojlib/*.jar

After that I remove lib folder from my project and compile it without lib directory. Be careful don't package jar files in your project. My war file is 180KB now and I deploy it easily and I shouldn’t deploy 15 MB war file every time.

java, lib, tomcat, war file no comment

first wintery mountain climbing

by Hamid Reza Fahimi Madjd @ Dec 22, 2007

1. My wife and I went to first wintery mountain climbing on Friday. The weather was cold (around -6 C) but it's sunny. At first we had some problems with our crampons but i found their temper ;)

Everything was ok but when we was returning my knee got pain. One or two month ago I went to doctor and he said "it's not important , but you should strengthen your knee" !

Anyhow that was fantastic for us. You can see some pictures about that below.

2. Today my intellij IDEA made me crazy, when I compiled and ran my j2ee App, appeared situation as coma after one or two click on links! I couldn't understand what's wrong. God, help me :(

3. I found a page that lists all irregular verbs in English language, enjoy it.

intellij, mountain, java no comment