JSP Simple Examples

JSP Simple Examples Index 1. Creating a String In jsp we create a string as we does in a java. In jsp we can declare it inside the declaration directive or a scriptlet directive. String Length In java, Strings are objects that belong to class java.lang.String. A string is a sequence of simple characters. We can get the length of the string by using the method length() of java.lang.String. Declaring string array in java An array is the collection of same data type. Suppose if we have a declare an array of type String, then it will store only the String value not any other data type. When we have a closely related data of the same type and scope, it is better to declare it in an array. Multidimensional array java A two dimensional array can be thought as a grid of rows and columns. The first array will reflect to a row and the second one is column. int array Array is a collection of same data type. Suppose if we have declared an array of type int then the array will take only the int values and not any other data types. We can find find out the length of the variable by using the variable length . JSP string array String array cannot hold numbers or vice- versa. Arrays can only store the type of data specified at the time of declaring the array variable. Custom exceptions Custom Exception inherits the properties from the Exception class. Whenever we have declare our own exceptions then we call it custom exceptions. Throwing an exception All methods use the throw statement to throw an exception. The throw statement requires a single argument a throwable object. Here is an example of a throw statement. Arrayindexoutofboundsexception ArrayIndexOutOfBoundException is thrown when we have to indicate that an array has been accessed with an illegal index. printStackTrace in jsp printStackTrace is a method of the Throwable class. By using this method we can get more information about the error process if we print a stack trace from the exception. Runtime Errors Errors are arised when there is any logic problem with the logic of the program. Try catch in jsp In try block we write those code which can throw exception while code execution and when the exception is thrown it is caught inside the catch block. Multiple try catch We can have more than one try/catch block. The most specific exception which can be thrown is written on the top in the catch block following by the less specific least. Nested try catch We can declare multiple try blocks inside the try block. The most specific exception which can be thrown is written on the top in the catch block following by the less specific least. kilometers per liter to miles per gallon Kilometers per liter : The distance traveled by a vehicle which is running on gasoline or diesel fuel in a kilometer. Miles per Gallon: The distance traveled by a vehicle which is running on gasoline or diesel fuel in a mile. Ascii values table ASCII stands for American Standard Code for Information Interchange. Computers can only understand numbers, so an ASCII code is the numerical representation of a character such as @, #, $, and so on. ASCII was developed when non- printing characters were rarely used. life cycle of a jsp page Life of the the jsp page is just same as the servlet life cycle. After get translated the jsp file is just like a servlet. Page directive attributes A directive is a way to give special instructions to the container at page translation time. The page directive is written on the top of the jsp page. Html tags in jsp In this example we have used the html tag inside the println() method of the out implicit object which is used to write the content on the browser. Password Controls In this program we are going to know how the server determines whether the password entered by the user is correct or not. This whole process is controlled on the server side. Multiple forms in jsp The form tag creates a form for user input. A form can contain checkboxes, textfields, radio- buttons and many more. Forms are used to pass user- data to a specified URL which is specified in the action attribute of the form tag. Interface in jsp In interface none of its methods are implemented. All the methods are abstract. There is no code associated with an interface. In an interface all the instance methods are public and abstract. Interfaces are always implemented in the class. They add extra behaviors to the class. Inheritance in java with example Inheritance is one of the concept of the Object- Oriented programming. It allows you to define a general class, and later more specialized classes by simply adding some new details. Constructor inheritance Constructors are used to create objects from the class. Constructor declaration are just like method declaration, except that they do not have any return type and they use the name of the class. The compiler provides us with a default constructor to the class having no arguments. Abstract classes We does not make a object of the abstract class. This class must be inherited. Unlike interface the abstract class may implement some of the methods defined in the class, but in this class at least one method should be abstract. Using Super class Variables With Sub-classed Objects One of the strong features of java is that it is follows a OOPs concept, and one of the feature of OOP in java is that, we can assign a subclass object or variable to the variable of the superclass type. Log files Log files keeps a records of internet protocol addresses (IP), Http status, date, time, bytes sent, bytes recieved, number of clicks etc. Calculate a factorial by using while loop In this example we are going to find out the factorial of 12 by using the while loop. In while loop the loop will run until the condition we have given gets true. Calculating factorial After going through this example you will be understand how you can calculate the factorial by using recursion in jsp. To make a program on factorial, firstly it must be clear what is recursion. Celsius Fahrenheit Celsius is a unit to measure temperature scale on which water freezes at 0 degree and boiling point is 100 degree. This unit is discovered by Celsius in 1742, a Swedish astronomer and physicist, he has invented the centigrade, or Celsius thermometer divided between the freezing and boiling points of water into 100 parts. comment in jsp In a jsp we should always try to use jsp- style comments unless you want the comments to appear in the HTML. Jsp comments are converted by the jsp engine into java comments in the source code of the servlet that implements the Jsp page. Html tag inside out implicit object In this program we are going to use a html tag inside a out object. out object is used to display the content on the browser. To make this program run use out object inside which define some html code along with the content you want to display on the browser Jsp methods In this example we are going to show you how we can declare a method and how we can used it. In this example we are making a method named as addNum(int i, int b) which will take two numbers as its parameters and return integer value. Multiple methods Jsp is used mainly for presentation logic. In the jsp we can declare methods just like as we declare methods in java classes. Methods can be declared in either declaration directive or we can declare it in scriptlet. If we declare method inside declaration directive, then the method is applicable in the whole page. Passing Array method Array is a collection of similar data type. It is one of the simplest data structures. Arrays holds equally sized data elements generally of the similar data type. Two index In this example we will show how we can use two indexes in a for loop. We can solve this problem by using for loop defined inside the scriptlet directive. Date in JSP To print a Date in JSP firstly we are importing a class named java.util.Date of the package java.util. This package is imported in the jsp page so that the Date class and its properties can accessed in the JSP page. If- Else Ladder A ladder means a vertical set of steps. It is a computer generated list of pairings used in eliminations. Nested If We use the if condition to check if the particular condition is true then it should perform a certain task, and if a particular condition is not true then it should do some other tasks. Quintessential JSP Quintessential means representing the perfect example of a class or quality. It is pure and concentrated essence of a substance. Include File JSP using directive and include action <%@ include file = " "%>: - This is include directive. This directive has only one attribute named as file, which is used to include a file in the jsp page at the translation time. <jsp:include page = " ">:- This is known as the include standard action. This standard action is used to include a file at run time. This standard action is evaluated at the run time. Snoop in JSP It mostly contains the request information, ServletContext initialization parameters, ServetContext attributes, request headers, response headers etc. sendRedirect In JSP sendRedirect() method is a method of HttpServletResponse interface. In sendRedirect() the object of request will be generated again with the location of page which will perform the request of the client. Request Header in JSP Whenever an http client sends a request, it sends the request in the form of get or post method or any other HttpRequest methhods. It can also sends the headers with it. Specific request headers in JSP Whenever an http client sends a request, it can also sends the headers with it. All the headers are optional except Content-length, which is required only for POST request. Java class in JSP To use the class inside the jsp page we need to create an object of the class by using the new operator. At last use the instance of the class to access the methods of the java file. Setting Colors in JSP In Jsp also we can set the background color which we want, the font color can be changed. The table can be coloured . By using the colors code we can give colors according to our wish. Sine Table in JSP Mathematically, the sine of an angle is the ratio of the length of the opposite side to the length of the hypotenuse of an imaginary right triangle having that angle in it. Applet In Jsp Applets are small programs or applications written in java. These applets are those small programs that runs on web browsers, usually written in java. We can use the applets in jee also. In jee it runs on the context of web application on a client computer. Creating a Local Variable in JSP Consider a situation where we have to declare a variable as local, then we should declare the methods and variables in tag except the declaration directive. Method in Declaration Tag Anything which will be declared inside declaration tag will be applicable within the whole application. We call this tag a Declaration Tag. The syntax of this tag is <%! --------- %>. Forward a JSP Page The request object goes to the controller then the controller decides by which jsp or servlet this request will be processed, then the request object is passed to that jsp or servlet and the output is displayed to the browser by the response object. Random in JSP Random numbers are the numbers that are determined entirely by chance. User does not have any control over the working of random numbers. random() is a method of Math class which extends java.lang package. JSP include directive By using the include tag the file will be included in the jsp page at the translation time. In this example we have created a jsp file which has to be included in the other jsp file by using the tag <%@ include file = " "%>. Literals in JSP Literals are the values, such as a number or a text string, that are written literally as part of a program code. A literal is a expression of a value, including a number or a text string. Passing Parameter using <jsp: param> Request parameters can be passed by using <jsp: param>. This tag contains two attributes: 1) name 2) value. Tag Handler Custom tags are usually distributed in the form of a tag library, which defines a set of related custom tags and contains the objects that implement the tags. Custom tag libraries allow the java programmer to write code that provides data access and other services, and they make those features available to the jsp author in a simple to use XML- like fashion. UseBean Syntax: <jsp:useBean id= "nameOfInstance" scope= "page | request | session | application" class= "package.class" type= "package.class > </jsp:useBean>. Expression Language In JSP EL means the expression language , it is a simple language for accessing data, it makes it possible to easily access application data stored in JavaBeans components. EL Basic Arithmetic Addition (+), subtraction (-), multiplication (*), division (/ or div), and modulus (% or mod) are all supported in Expression Language. Error conditions, like division by zero are handled easily by the expression language.