Building a Web Application Using EJB, JPA, and JavaServer Faces – Annotations

Any symbol in Java code beginning with @ is known as an annotation.  

The use of annotations allows you to add metadata to your objects. Examples of annotations follow:

Annotation	Description
@Entity	Identifies the file as an EJB 3.0 entity
@NamedQuery	A query that can be used at run time to retrieve data
@Table	Specifies the primary table for the entity
@Id	Can define which property is the identifier for the entity
@Column	Specifies a mapped column for a persistent property or field
@ManyToOne	Specifies a type of foreign key relationship between tables
@JoinColumn	Specifies the join column and referenced column for a foreign key relationship

Installing Apache Maven-Java tool

Download maven.

Windows OS:

1. Unzip the distribution archive, i.e. apache-maven-3.0.4-bin.zip to the directory you wish to install Maven 3.0.4. These instructions assume you chose C:\Program Files\Apache Software Foundation. The subdirectory apache-maven-3.0.4 will be created from the archive.
2. Add the M2_HOME environment variable. [almost similar as this]: adding the M2_HOME variable in the user variables with the value C:\Program Files\Apache Software Foundation\apache-maven-3.0.4. Be sure to omit any quotation marks around the path even if it contains spaces.
3. In the same dialog, add the M2 environment variable in the user variables with the value %M2_HOME%\bin.
4. In the same dialog, update/create the Path environment variable in the user variables and prepend the value %M2% to add Maven available in the command line.
5. In the same dialog, make sure that JAVA_HOME exists in your user variables or in the system variables and it is set to the location of your JDK, e.g.C:\Program Files\Java\jdk1.5.0_02 and that %JAVA_HOME%\bin is in your Path environment variable.
6. Open a new command prompt and run mvn –version to verify that it is correctly installed.

Linux based/Ubuntu Operating Systems:

1. Extract the distribution archive, to the directory you wish to install Maven 3.0.4. These instructions assume you chose /home/username/java/tools/maven.
2. Open terminal and type:  gedit ~/.bashrc
3. Set environment variable by adding the following lines at the bottom of .bashrc :
   •  export M2_HOME=/home/username/java/tools/maven
   • export M2=$M2_HOME/bin
   • export PATH=$M2:$PATH
   • export JAVA_HOME=/usr/lib/jvm/jdk-default #if JAVA_HOME not exist.
4. Run mvn –version to verify that it is correctly installed.

How to create non-editable JTable:

Override the method “isCellEditable” and implement as needed, such as:

//instance table model
DefaultTableModel tableModel = new DefaultTableModel(){
   @Override
   public boolean isCellEditable(int row, int column) {
      return false;
   }
};
//...others
table.setModel(tableModel);

Protected: System.getProperty(key) key list for Java with value:

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System.getProperty(key) key list for java:

 

java.version	Java Runtime Environment version
java.vendor	Java Runtime Environment vendor
java.vendor.url	Java vendor URL
java.home	Java installation directory
java.vm.specification.version	Java Virtual Machine specification version
java.vm.specification.vendor	Java Virtual Machine specification vendor
java.vm.specification.name	Java Virtual Machine specification name
java.vm.version	Java Virtual Machine implementation version
java.vm.vendor	Java Virtual Machine implementation vendor
java.vm.name	Java Virtual Machine implementation name
java.specification.version	Java Runtime Environment specification version
java.specification.vendor	Java Runtime Environment specification vendor
java.specification.name	Java Runtime Environment specification name
java.class.version	Java class format version number
java.class.path	Java class path
java.library.path	List of paths to search when loading libraries
java.io.tmpdir	Default temp file path
java.compiler	Name of JIT compiler to use
java.ext.dirs	Path of extension directory or directories
os.name	Operating system name
os.arch	Operating system architecture
os.version	Operating system version
file.separator	File separator (“/” on UNIX)
path.separator	Path separator (“:” on UNIX)
line.separator	Line separator (“\n” on UNIX)
user.name	User’s account name
user.home	User’s home directory
user.dir	User’s current working directory

 

Installing Oracle-JDK in Ubuntu

Download JDK from ORacle. Run Terminal:

chmod u+x jdk-6u31-linux-i586.bin
./jdk-6u31-linux-i586.bin
sudo mv jdk1.6.0_31 /usr/lib/jvm/

#Next line will add java to symlink

sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.6.0_31/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.6.0_31/bin/javac" 1

Or, you can set environment variable by adding the following lines at the bottom of .bashrc by “gedit ~/.bashrc”:

export JAVA_HOME=/usr/lib/jvm/jdk1.7.0_03
export PATH=$PATH:$JAVA_HOME/bin

You can now check if the java is installed properly in terminal:

java -version
javac -version

These will return the version of java and javac.

Generics are not supported in -source 1.3 error in Maven Project

When compiling via maven project, you may have encountered following error:

generics are not supported in -source 1.3 error in Maven Project. use -source 5 or higher to enable generics.

Annotation is not allowed in -source 1.3 use -source 5 or higher to enable annotation.

To solve this you must add the below lines at your pom.xml :

<build>
 <plugins>
  <plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-compiler-plugin</artifactId>
   <configuration>
    <source>1.5</source>
    <target>1.5</target>
   </configuration>
  </plugin>
 </plugins>
</build>

RMI plug-in for Eclipse

RMI plug-in from Genady. This tool is for the development of RMI in eclipse.

How to install Genady plug-in:

1. Save your work and exit  from Eclipse.
2. Delete previous version if installed any.
3. Download the plu-in zip from here.

How to Set Path Variable in Windows 7

a. Checking  if java is set as path environment variables:

1. Go to Start-> Run-> cmd

2. write: java -version and hit Return. If the path variable set properly it will show your java version.

b. Setting path variable in windows 7:

1. Go to start menu -> control panel -> system and security -> System.
or simply paste this in your windows explorer address bar–>
Control Panel\System and Security\System

2. Now select “Advanced system settings” from the left panel.

3. A new window appears. Click on “Environment variables…”
4. under System Variables, find PATH, and click on it.
 
5. If you do not have the item PATH, you may select to add a new variable and add PATH as the name and the location of the class as the value. 

6. the location looks like: “C:\Program Files (x86)\Java\jdk1.6.0_23\bin;” end it with a semicolon.

7. Click ok. 

8. Close all these windows.

C. Check if path variable is set properly:

1. Go to Start-> Run-> cmd

2. write: “java -version” end hit Return. if the path variable set properly it will show your java version.

3. If it still not working reboot your computer and try step c1 & c2.

Hope, now your path variable for java is set. Else read steps of “b” carefully.