JSP Simple Examples

# 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.


  1. EL Basic Comparisons
    The Expression Language has the following Basic Comaparisions: 
    < >   <=   >=   lt   gt le  ge
    = =  !=   eq  ne
    && and
    ||  or
  2. EL Implicit Objects
    EL is the JSP 2.0 Expression Language Interpreter from Apache Corporation. EL means the expression language , it makes it possible to easily access application data stored in JavaBeans components. 
  3. Implementing Conditional Content on a JSP Page
    We make use of the condition to check if the entered value is correct. It correct then what will be the output, and in case if it is wrong then what output will be displayed to the browser.
  4. Exception Handling in JSP
    An exception can occur if you trying to connect to a database which doesn't exists or the database server is down, it may be thrown if you are requesting for a file which is unavailable, then the exception will be thrown to you. 
  5. Generate Error In JSP
    In software engineering, the term refers to an incorrect action or calculation performed by software. In general we can say that the error results from a combination of a defect and a fault.
  6. Using Operators In JSP
    In mathematics, an operator is a function, usually of a special kind depending on the topic. An operator is a function that acts on functions to produce other functions. A operator symbol or operator name is a notation that denotes a particular operator. 
  7. Precompiling a JSP Page
    Some jsp containers support the capability of precompiling a JSP page. To precompile a jsp page, access the page with a query string of ?jsp_precompile. This we will write in the URL.
  8. JSP Plugin
    Syntax: <jsp: plugin type = "bean |applet" code = "ClassFileName" codeBase = "ClassFileDirectoryName">
  9. Using Protected Access in JSP
    In java there are three types of access specifiers: public, protected, private. We always declare access specifiers to be more accessible.
  10. Conditional Forward using EL
    We can forward one page to another jsp page, html page or any other servlet page. A condition is checked before forwarding the page to
    another page. 
  11. Request Parameters In EL
    In EL we use "param" attribute to read the parameters from the file. If we have multiple values to read from the same field then we will use "paramValues".
  12. Request Headers In EL
    Whenever an http client sends a request, it also sends the headers with it. All the headers are optional except Content-length, which is required only for POST requests.
  13. Break Statement in JSP
    The use of break statement is to escape early from the loop. It allows the program to escape from the for, while, switch and do while loops. A break may only appear on one of these statements
  14. Finding Average in JSP
    In mathematics, an average is a measure of the middle of the data set. The average value is the total amount divided by the total number of elements.
  15. Midpoint of two number
    While solving any mathematical problem it becomes important to find the number that is exactly between two numbers. 
  16. While Loop in JSP
    The while loop is a control flow statement, which allows code to be executed repeatedly based on the given boolean condition. In while loop the condition is firstly evaluated, if it finds that the condition is true, then the code will be executed. 
  17. Using Beans And Page Scope
    The scope in which the Bean exists and the variable named in id is available. The  default value of scope is page. In this bean object is placed in the PageContext object and the object can be accessed within the page only.
  18. Using Beans And Request Scope
    request scope:
    In this scope bean object is placed in the ServletRequest object for the current request only.
  19. Using Beans And Session Scope
    session scope:
    In this the bean will get stored in the HttpSession object associated with the current session.
  20. Using Beans And Application Scope
    application scope:
    In this the bean will get stored in the ServletContextServletContext is shared by all servlets in the same web application.
  21. EL and Complex Java Beans
    Java Beans: They are platform- independent component and usable software programs which you can use develop and assemble easily to create complex applications. JavaBean are also known as beans.
  22. EL and  Complex Java Beans1
    means the expression language , EL provides us a way to access the java code. EL is such a language which is liked by java programmers as well as by those who are not programmers like designers.
  23. Use of dot(.) operator in EL
    We use dot(.) operator within EL to access properties of bean and map values. For example in the EL ${useOfDotOperator.name}, the left hand side variable will be a map value or a bean. The thing to the right of the dot operator must be a Map key or a bean property
  24. Using [ ] operator of EL with an Array
    An array is a type of container which can hold a fixed number of values of a single type. Array is a collection of similar data types. It means if you have declared an array as string then it can only store the string values. 
  25. Using [ ] operator of EL with the ArrayList
    ArrayList is resizable array implementation of the List interface. As the elements are increased in an ArrayList, its capacity also grows automatically. It can store all type of elements including null.
  26. Using [ ] operator of EL with the Map
    stores the values in the form of a key- value pair. Map can't have a duplicate keys, and each key is associated with at least one value. In map we can retrieve the value by using ${map["0"]}.
  27. How to Use Java Functions In EL
    EL to invoke a function:
    We can call the function by using ${prefix:name()}. This name() we have defined in the <name> tag inside the <function> tag.
  28. Catch an Exception using EL
    In this example we are going to catch an exception by using the EL. We can't prevent errors, but of course we can give the user a friendlier error response page. Instead of giving any error codes we should try to show some friendly messages. 
  29. Convert string to Date in JSP
    To parse a string to a date we use a class named SimpleDateFormat. In the constructor of this class we define the date format we required and ask the user to enter the date in the same format. 
  30. <c:forEach> in JSTL
     <c:forEach> tag is a simple way to iterate over arrays and collections. This tag is very much similar to for loop. The tag repeats the body of the tag for each element in the array or collection.
  31. Nested <c:forEach> in JSTL
    tag is a simple way to iterate over arrays and collections. This tag is very much similar to for loop. The tag repeats the body of the tag for each element in the array or collection. The nested <c:forEach> is same as loop inside the loop. This tag can be used for more complex loops.
  32. JSTL: another for each and status
    In this program we have used the directive to set the attributes of a bean. This attribute is retrieved by the item attribute of the <c: forEach> tag. The LoopTagStatus class has a count property which gives us the current value of the iteration counter.
  33. JSTL: forEach and status
    It is not a good programming practice to use directive to set the attribute in a bean or a map when we using the jstl. We can do it by using the <c:set> tag of jstl. In this program we are going to use the tag <c: set>.
  34. JSTL for Loop <c: forEach>
    In the tag <c:forEach var="i" begin="1" end="20" step="1" varStatus ="status">. Here this tag is working exactly as for loop works in a jsp or in java. i is the name of the variable, which begins from 1 and continues upto 20.
  35. Conditional Include with <c:if>
    Imagine if we want to check that the value entered by the user is fulfilling the condition or not, then in these condition the <c:if> tag is used. This tag will not work if the value entered by the user doesn't match any of the condition given in the program.
  36. <c:If> with No Body
    The <c:if> tag is not for applicable if we want to do one thing if the condition is true, and another thing if the condition is false. In this situation this tag will become obsolete.
  37. JSTL If- Else
    The problem with <c:if> is that, this tag will not work if the value entered by the user doesn't match any of the condition given in the program. In this tag there is no way to specify the default value. Here comes the use of  the <c:choose> tag.
  38. Comparing Two String with <c:if>
    In this program we are making use of <c:if>, in which we are going to check whether the given string is equal to another string, the case of the string will be ignored.
  39. <c:forTokens>
    <c:forTokens items="${string}" delims="!," var="tokenName" varStatus="status">.
    This tag is used is for making tokens a string. It iterates over tokens generated, which is separated by the supplied delimiters.
  40. <c: out> in JSTL
    In this example we have used only one attribute i.e. value. It is a must attribute in the tag. We are just calculating the multiplication of two numbers by using the <c: out> core action tag.
  41. <c: out> attribute default
    We can use this attribute if the resulting value is null. In this example we are just printing the value of the default attribute on the browser.
  42. <c: out> attribute escapeXml
    attribute takes a boolean value and is used to check whether there is any need to convert the &, <, > etc to their character encoding codes.
  43. <c: out> For Simple Calculation and Output
    In this example we have used only one attribute of <c: out>. The attribute value which is a must attribute and by using this attribute we are calculating the sum of numbers and displaying the output on the browser. 
  44. Listing HTTP Headers
    In this example we are going to list the headers of the HttpServletRequest object. We are using the <c: forEach> tag. The items in the header get stored in the attribute var of the jstl core library. Now the value will be displayed to the user by using the core library tag <c: out>.
  45. <c: url> in JSTL
    By using the <c: url> we are doing the URL rewriting but by using the <c: param> core action tag inside the <c: url> our requirement for URL rewriting and URL encoding get fulfilled. 
  46. Creating URL using <c:url>
    In this example we are going to use one html page from which we are going to enter the parameters which we want to append to the URL. The second page will be a jsp page in which we are going to retrieve the value passed in the html page and in the third we are going to displaying those values.
  47. JSTL <c:import>
    The disadvantage of using the <jsp:include> or the include directive is that we can only include the content or files which are the part of the current web application. But by using the jstl <c:import> we can also include those contents or files which are not a part of the current web application but lying somewhere outside the web application.
  48. JSTL <c:import> with <c:param>
    In the program we have also used the <c:param> core action tag which is a child of the <c:import>. The <c:param> takes two attributes, one is name and the second one  is the value. The tag <c:param> is used to customize the thing which we want to include. 
  49. Throwing an Exception in JSTL
     In this program we are going to show you what will happen if we try to divide any number by 0. After going through this example you can better understand how the exception can be thrown in JSTL.     
  50. JSTL <c: catch>
    If we have any doubt that the particular code can invoke a error then we should write those codes inside the <c:catch> core action tag. The beauty of this tag is that it works both like a try and catch.
  51. Catching Exception using c: catch
    If you have written some code which you think that it can invoke a error, and still you are confident that you can recover from that solution by yourself. Then then is one tag provided to you that is <c:catch>.
  52. Catching Exception using c: catch and c:set
    In this tag we are defining the attribute of the <c:catch> core action tag that is var. This attribute is optional and is used when we want to access the exception after the end of the <c:catch> tag. 
  53. JSTL c:catch with c:if
    By performing simple mathematical calculation we are going to teach how can we handle the exception by using the <c: if> tag. 
  54. JSTL : Submit Form TextField
    In this example we are going to see how we can retrieve multiple values from the form. 
  55. JSTL: Set Session Attribute
    Consider a situation where we are using the jstl and there is a need to set a variable in the session. You all know that it can be done very easily in the servlets and jsp, but what about jstl. Don't worry it can be done very easily in the jstl as compared to servlets and jsp.
  56. JSTL: Removing Session Attribute
    In this example we are going to remove the session attribute which we have set in the session. For this we are going to use the core action library, so we need to use the jstl core library provided by the Sun MicroSystems in our example. 
  57. JSTL: Property Access 
    In this example we are going to show we can access the property by using  the dot(.) and [ ] operator. 
  58. JSTL: String Collection
    In this example we are going to set some movies in the attribute var. The var attribute in <c:set> is used for setting attributes variables.  It works like <jsp:setProperty> tag but by using <jsp:setProperty> we can only set the property of a bean.
  59. JSTL: Form Action Text Field
    In this example we are going to retrieve the value we have entered in the jsp form. 
  60. Using JSTL For Finding Square
    In this program we are going to find out the square of values from 1 to 10. But the approach we are taking to finding out the square is the JSTL. 

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