JSF - Java Server Faces Tutorials
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Industries use frameworks for application development quite often. For example: Java concepts like JSP, Servlet, Swing, Bean, JDBC can be used directly to create web-applications but when such applications become big, it becomes difficult to maintain and develop them further. Hence, frameworks like struts are used to develop large web-based Java applications. This makes maintenance and further development easier. If you need to write a very simple web application with a few pages, then you might consider using JSP/Servlet directly otherwise Struts like frameworks are better options. Struts-1 uses the concept Model View Architecture (MVC) and provides the controller. In MVC model, Model represents business logic, View represents user interfaces, and Controller represents/controls control flow of the application. Struts' control layer is based on standard technologies like Java Servlets, JavaBeans, ResourceBundles, and XML, as well as various Apache Commons packages, like BeanUtils and Chain of Responsibility. For the Model, struts-1 framework can interact with standard data access technologies, like JDBC and EJB, as well as most any third-party packages, like Hibernate, iBATIS, or Object Relational Bridge. For the View, the framework works well with JavaServer Pages, including JSTL and JSF, as well as Velocity Templates, XSLT, and other presentation systems. The framework's Controller acts as a bridge between the application's Model and the web View. When a request is received, the Controller invokes an Action class. The Action class consults with the Model to examine or update the application's state. The framework provides an ActionForm class to help transfer data between Model and View. Struts-1 Configuration ----------------------- web.xml is one of the configuration files. It is an XML-formatted file that works as a deployment descriptor. struts-config.xml is another resource file to initialize the applications resources. These resources include ActionForms to collect input from users, ActionMappings to direct input to server-side Actions, and ActionForwards to select output pages. Sample struts-config.xml file. ?xml version="1.0" encoding="ISO-8859-1" ?> Other resources like Validators can be initialized here.
10 Database Design Tips 1. Develop A Prototype 2. Split database structure into multiple tables 3. Use understandable field names 4. Avoid illegal file names 5. Ensure Consistency 6. Avoid blank fields 7. Use standard descriptors for date and time 8. Use currency fields if appropriate 9. Avoid proprietary extensions 10. Avoid the use of field dividers
Microsoft Visio, and dbVisualizer provide features to create ER diagrams from existing database tables.
Why needed?
In early days many companies did not create documentation/ER diagrams for their databases. However, ER diagram is very useful to understand the total database structure that helps a new programmer to work on the database more efficiently.
Visio:
While creating Database diagrams, a menu item named database is displayed. Reverse Engineering option under Database menu helps to create ER diagram from existing database tables. Before that, target database drivers for visio need to be installed. If the database is in db2/mysql/postgresql, then db2/mysql/postgresql drivers for visio should be installed. From Database/options/drivers, the driver needs to be configured. Afterwards, Reverse Engineering option may be used to create the ER diagram. There is no suitable driver for postgresql databses for Visio. ODBC drivers may be used for the purpose (the ER diagram may not be accurate from ODBC driver for postgresql).
dbVisualizer:
In dbVisualizer, when the TABLEs group/option is selected in the left pane in the right/middle pane there will be a references option. When the references tab is selected, an ER diagram is displayed using all tables. The ER diagram can be displayed as Hierarchical, circular, orthogonal, or organic. There are options for the purpose.
When a single table name is selected, the table and the associated tables are displyed in an ER diagram.
In the rightest column, selected tables option allows to create ER diagrams only for the selected tables. When ’selected tables’ is clicked a list is displayed in a dialogbox. Tables can be selected from this list (use control key). Build graph option creates and displays the ER diagram.
If I worked with a programmer who looked busy all the time, I’d assume that he was not a good programmer
because he wasn’t using his most valuable tool, his brain. — Steve Mcconnell
Personal Character and Programming
———————————-
For a software engineer the only building material is the human intellect and the primary tool is he himself.
Character is the more decisive factor than intelligence in the make up of a superior programmer.
The best programmers of the world are the most humble. They realize how small their brain is for programming
and they agree their limitations.
Being humble gives opportunities to learn more about programming
Human brain is really limited to understand an average program fully. So what better programmers do (adopt better habits) are:
1. Decompose systems into smaller sub-systems. Write short routines. It reduces load from the brain
2. Good programmers review, inspect, and test their codes/designs to compensate for brain limitations
3. Good programmers follow standard and proven conventions to reduce load from their brain
Ways to be a good programmer:
Curiosity is important
Experiment
Read about problem solving
Read books and periodicals
Read case studies
Network with other programmers
Adopt good programming habits
Avoid laziness
Experince, persistence, and guts are sometimes hurtful to the programmers
To be a good programmer developing the right programming habits is the most important strategy
Key Strategies in Software Debugging
1. Understand the requirements well. Design the software well. Code well. It will reduce the number of defects in your system.
2. Don’t use random guessing about defects. Use a systemetic and scientific method to detect and fix bugs.
3. Identify the root cause of a defect. Understand the program and then try to solve
4. Set the compiler warning in it’s pickiest level. Solve all the issues as listed in the warning messages
5. Make wise use of debugging tools but use your brain in parallel
Debugging?
Is a process to find the cause of an error/issue/defect wheras testing is the process to find the error/defect in the first place.
Defects are opportunities for a good programmer. How?
When you are a good programmer, you will code well.
Still if you have defects than something is missing somewhere,
it will give you opportunities to learn many stuffs like:
1. Check: Did you understand the program/requirements?
2. Learn: what kinds of mistakes you make
3. Learn: how you solve problems
4. How you fix defects
When you know your own patterns then there will be opportunities to improve yourself.
Bad ways to debug software:
1. Find defects by random guessing, by using print statements randomly.
2. Don’t try to understand the program just find the defect and fix
3. Use most obvious fix. You see the code does not work for 23 as input otherwise fine. So write a special case for 23
4. Debugging by superstition.
Finding a Defect
Scientific method of debugging
1. Stabilize the error through experiments. Be sure about the error and when it happens.
2. Gather the data through repeatable experiments that produces the defect
3. Form a hypothesis that states the cause of the error
4. Design experiments to prove or disprove the hypothesis.
5. Prove or disprove the hypothesis.
6. Repeat as needed
7. Fix the defect
8. Test the fix
9. Look for similar errors in your code.
Checklist for finding defects:
Reproduce the same error in several different ways.
Brainstorm for possible hypotheses
Use a notepad to list the things to try
Find the suspicious region of your code
Check the error-prone classes and routines
Check recently modified/added codes
Check for common defects
Check region by region. Expand your region after one region is covered
Talk to someone about the problem
Relax a bit. It works great sometimes.
[but if your boss sits just behind you to watch your screen, to follow your each key press and mouse move, and
he does not understand the point of relaxing a bit,
THEN YOU ARE in trouble]
1. Open the file with the File class;
2. Create a FileInputStream object using the File object;
3. Convert the FileInputStream to a BufferedInputStream to greatly increase file reading speed;
4. Convert the BufferedInputStream to a DataInputStream; the methods of DataInputStream give me a fair amount of flexibility in reading the data.
5. Read the file until the end
File f = new File("mydata.txt");
FileInputStream fis = new FileInputStream(f);
BufferedInputStream bis = new BufferedInputStream(fis);
DataInputStream dis = new DataInputStream(bis);
String record = null;
try {
while ( (record=dis.readLine()) != null ) {
//
// put your logic here to work with "record"
//
}
} catch (IOException e) {
//
// put your error-handling code here
//
}
A good example: http://developerlife.com/tutorials/?p=25
Another very good example: http://www.developerfusion.co.uk/show/2064/: I followed this code to extract attribute values from an xml file.
CVS Version Control System:
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