Jsp in Servlet by Rj
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The document provides an overview of JavaServer Pages (JSP) technology. It discusses how JSP pages allow mixing static HTML content with server-side Java code to create dynamic web pages. JSP pages are compiled into Java servlets, which generate the HTML responses. The document covers JSP syntax elements like scriptlets, expressions, and directives that allow embedding Java code in JSP pages. It also discusses JSP lifecycle phases like translation, compilation, execution and cleanup. Common JSP actions like include, forward, plugin and working with JavaBeans are also summarized.
![Syntax for Expression LanguageSyntax for Expression Language
(EL)(EL)
${ expression }
Here, expr specifies the expression
itself.
The most common operators in JSP EL
are . and [].
These two operators allow you to access
various attributes of Java Beans and built-
in JSP objects.](https://image.slidesharecdn.com/jspbyrj-180803094000/85/Jsp-in-Servlet-by-Rj-65-320.jpg)
Jsp in Servlet by Rj
- 1. UNIT - 3UNIT - 3 • JSP Basic Syntax, •HTMLText, HTML comments, •TemplateText, •JSP Comment, JSPExpression, •JSP Scriptlet, •JSP Declaration, JSP Directives, •JSP Action, JSP Expression Language Element, •CustomTag (Custom Action), •EscapedTemplateText, Using JSP Scripting
- 2. JSP (JavaServer Page)JSP (JavaServer Page) JSP is a server side technology that does all the processing at server. It is used for creating dynamic web applications, using java as programming language. JSP’s allow us to separate the dynamic content of webpage from static presentation content. A JSP page consists of HTML tags and JSP tags. HTML tags are used to create static page content and JSP tags are used to add dynamic content to web pages. JSP pages are compiled into a Java Servlet by a JSP translator. A JSP page consists of HTML tags and JSP tags. The jsp pages are easier to maintain than servlet because we can separate designing and development. It provides some additional features such as Expression Language, Custom Tag etc.
- 3. Basically, any html file can be converted to JSP file by just changing the file extension from “.html” to “.jsp”, it would run just fine. JSP tag is … <% … %> What differentiates JSP from HTML is the ability to use java code inside HTML. In JSP, you can embed Java code in HTML using JSP tags. for e.g. run the code below, every time you run this, it would display the current time. That is what makes this code dynamic.
- 4. Save it with .jsp & put inside a folderSave it with .jsp & put inside a folder and put that folder in webapp dirand put that folder in webapp dir <HTML> <BODY> Hello BeginnersBook Readers! Current time is: <%= new java.util.Date() %> </BODY> </HTML> <html> <body> <% out.print(2*5); %> </body> </html>
- 5. Directory structure of JSPDirectory structure of JSP
- 6. Jsp vs htmlJsp vs html HTML JSP 1 Html is given by w3c (World Wide Web Consortium). JSP is given by SunMicro System. 2 Html generated static web pages. JSP generated dynamic web pages. 3 It do not allow to place java code inside Html pages. JSP allows to place java code inside JSP pages. 4 It is Client side technology It is a Server side technology. 5 Need Html Interpreter to execute these code. Need JSP container to execute jsp code. 6 It does not allow to place custom tag or third party tag. It allow to place custom tag or third party tag.
- 7. JSP SERVLET 1 JSP is a webpage scripting language that can generate dynamic content. Servlets are Java programs that are already compiled which also creates dynamic web content. 2 JSP run slower compared to Servlet as it takes compilation time to convert into Java Servlets. Servlets run faster compared to JSP. 3 It’s easier to code in JSP than in Java Servlets. Its little much code to write here. 4 In MVC, jsp act as a view. In MVC, servlet act as a controller. 5 JSP are generally preferred when there is not much processing of data required. servlets are best for use when there is more processing and manipulation involved. 6 The advantage of JSP programming over servlets is that we can build custom tags which can directly call Java beans. There is no such custom tag facility in servlets. 7 We can achieve functionality of JSP at client side by running JavaScript at client side. There are no such methods for servlets. 8 JSP is java in html. Servlet is html in java
- 8. Life Cycle of JSPLife Cycle of JSP JSP pages follow these phases: Translation of JSP Page Compilation of JSP Page Classloading (class file is loaded by the classloader) Instantiation (Object of the Generated Servlet is created). Initialization ( jspInit() method is invoked by the container). Reqeust processing ( _jspService() method is invoked by the container). Destroy ( jspDestroy() method is invoked by the container).
- 10. As depicted in the above diagram, JSP page is translated into servlet by the help of JSP translator. The JSP translator is a part of webserver that is responsible to translate the JSP page into servlet. Afterthat Servlet page is compiled by the compiler and gets converted into the class file. Moreover, all the processes that happens in servlet is performed on JSP later like initialization, committing response to the browser and destroy.
- 11. JSP Page Translation:In the first step, the web container translates the JSP file into a Java source file that contains a servlet class definition. The web container validates the correctness of JSP pages and tag files. JSP Page Compilation:In the second step, the web container compiles the servlet source code into a Java class file. JSP Page Class Loading:In the third step, the servlet class byte code is loaded into the web container’s JVM software using class loader. JSP Page Servlet Instance:In the fourth step, the web container creates an instance of the servlet class.
- 13. JSP Compilation:JSP Compilation: When a browser asks for a JSP, the JSP engine first checks to see whether it needs to compile the page The compilation process involves three steps: ◦ Parsing the JSP. ◦ Turning the JSP into a servlet. ◦ Compiling the servlet.
- 14. JSP Initialization:JSP Initialization: When a container loads a JSP it invokes the jspInit() method before servicing any requests
- 15. JSP Execution:JSP Execution: This phase of the JSP life cycle represents all interactions with requests until the JSP is destroyed.
- 16. JSP Cleanup:JSP Cleanup: The destruction phase of the JSP life cycle represents when a JSP is being removed from use by a container. The jspDestroy() method is the JSP equivalent of the destroy method for servlets
- 17. JSP Scriptlet tagJSP Scriptlet tag (Scripting elements)(Scripting elements) In JSP, java code can be written inside the jsp page using the scriptlet tag
- 18. JSP Scripting elementsJSP Scripting elements The scripting elements provides the ability to insert java code inside the jsp. There are three types of scripting elements: 1. scriptlet tag <% … %> 2. expression tag <%= … %> 3. declaration tag <%! … %>
- 19. JSP scriptlet tagJSP scriptlet tag A scriptlet tag is used to execute java source code in JSP. Syntax is as follows: ◦ <% java source code %>
- 21. Example of JSP scriptlet tagExample of JSP scriptlet tag
- 23. JSP expression tagJSP expression tag The code placed within JSP expression tag is written to the output stream of the response So you need not write out.print() to write data. It is mainly used to print the values of variable or method.
- 27. JSP Declaration TagJSP Declaration Tag The JSP declaration tag is used to declare fields and methods. The code written inside the jsp declaration tag is placed outside the service() method of auto generated servlet
- 29. JSP Scriptlet tag vs DeclarationJSP Scriptlet tag vs Declaration tagtag
- 34. JSP Action TagsJSP Action Tags There are many JSP action tags or elements. Each JSP action tag is used to perform some specific tasks. The action tags are used to control the flow between pages and to use Java Bean
- 36. Using Standard Actions TagsUsing Standard Actions Tags 1. <jsp:plugin> 2. <jsp:forward> 3. <jsp:include>
- 37. <jsp:include> action Tag<jsp:include> action Tag The jsp:include action tag is used to include the content of another resource it may be jsp, html or servlet. The jsp include action tag includes the resource at request time so it is better for dynamic pages because there might be changes in future. The jsp:include tag can be used to include static as well as dynamic pages
- 38. Advantage ◦ Code reusability : ◦ We can use a page many times such as including header and footer pages in all pages. So it saves a lot of time
- 40. Example of <jsp:include> actionExample of <jsp:include> action tagtag
- 45. <jsp:forward> action tag<jsp:forward> action tag
- 47. <jsp:plugin> Action tag<jsp:plugin> Action tag The plugin action is used to insert Java components into a JSP page. It determines the type of browser and inserts the <object> or <embed> tags as needed The <jsp:plugin> action tag is used to embed applet in the jsp file. The <jsp:plugin> action tag downloads plugin at client side to execute an applet or bean
- 48. When a jsp wants to display response in a graphics format in a browser, then a jsp page will integrates with an applet
- 51. <jsp:param><jsp:param> <jsp:param> tag is used to represent parameter value during jsp forward or include action this should be the sub tag of <jsp:forward> or <jsp:include> When an include or forward element is invoked, the original request object is provided to the target page. If you wish to provide additional data to that page, you can append parameters to the request object by using the jsp:param element
- 55. JavaBeansJavaBeans In computing based on the JavaPlatform, ◦ JavaBeans are classes that encapsulate many objects into a single object (the bean). ◦ They are serializable, have a zero-argument constructor, and allow access to properties using getter and setter methods The name "Bean" was given to encompass this standard, which aims to create reusable software components for Java
- 56. JavaBeans is ◦ an object-oriented programming interface from Sun Microsystems ◦ that lets you build re-useable applications or program building blocks called components ◦ that can be deployed in a network on any major operating system platform
- 59. jsp:useBean action tagjsp:useBean action tag The jsp:useBean action tag is used to locate or instantiate a bean class. If bean object of the Bean class is already created, it doesn't create the bean depending on the scope. But if object of bean is not created, it instantiates the bean
- 62. jsp:setPropertyjsp:setProperty and jsp:getProperty action tagsand jsp:getProperty action tags The jsp:setProperty action tag sets a property value or values in a bean using the setter method The jsp:getProperty action tag returns the value of the property.
- 64. Jsp expression language elementJsp expression language element JSP Expression Language (EL) makes it possible to easily access application data stored in JavaBeans components. JSP EL allows you to create expressions both (a) arithmetic and (b) logical. Within a JSP EL expression, you can use integers, floating point numbers, strings, the built-in constants true and false for boolean values, and null.
- 65. Syntax for Expression LanguageSyntax for Expression Language (EL)(EL) ${ expression } Here, expr specifies the expression itself. The most common operators in JSP EL are . and []. These two operators allow you to access various attributes of Java Beans and built- in JSP objects.
- 66. Custom Tag (Custom Action) Custom tags are user-defined tags. They reduces the possibility of scriptlet tag and separates the business logic from the JSP page. The same business logic can be used many times by the use of custom tag. Advantages of Custom Tags Eliminates the need of scriptlet tag The custom tags eliminates the need of scriptlet tag which is considered bad programming approach in JSP. Separation of business logic from JSP The custom tags separate the the business logic from the JSP page so that it may be easy to maintain. Re-usability The custom tags makes the possibility to reuse the same business logic again and again.
- 67. To create a custom tag we need three things: 1) Tag handler class: In this class we specify what our custom tag will do when it is used in a JSP page. 2) TLD file: Tag descriptor file where we will specify our tag name, tag handler class and tag attributes. 3) JSP page: A JSP page where we will be using our custom tag.
- 69. Tag handler class: A tag handler class should implement Tag/IterationTag/ BodyTag interface or it can also extend TagSupport/BodyTagSupport/SimpleTagSu pport class. All the classes that support custom tags are present inside javax.servlet.jsp.tagext. In the below we are extending the class SimpleTagSupport.
- 71. TLD File This file should present at the location: Project Name/WebContent/WEB-INF/ and it should have a .tld extension. Note: <name> tag: custom tag name. In this example we have given it as MyMsg <tag-class> tag: Fully qualified class name. Our tag handler class Details.java is in package beginnersbook.com so we have given the value as beginnersbook.com.Details.
- 73. Using custom tag in JSP Above we have created a custom tag named MyMsg. Here we will be using it. Note: taglib directive should have the TLD file path in uri field. Above we have created the message.tld file so we have given the path of that file. Choose any prefix and specify it in taglib directive’s prefix field. Here we have specified it as myprefix. Custom tag is called like this: <prefix:tagName/>. Our prefix is myprefix and tag name is MyMsg so we have called it as <myprefix:MyMsg/> in the below JSP page.
- 75. Predefined Variables in JSPPredefined Variables in JSP These variables can be used with servlets and Java beans. Following are the list of predefined variables. request: This variable specifies the data included in a http request. This variable takes value from the clients' browser to pass it over to the server.reponse: This variable specifies the data included in the http response. It is used with cookies and also in http headers. out: This variable specifies the output stream otherwise known as printwriter in a page context. session: This variable specifies the data associated with httpsession object with a specific session of a user. The main purpose of this object is to use the session information to maintain multiple page requests.
- 76. application: This variable is used to share data with all application pages. Config: This variable refers the java servlet configuration value. pagecontext: This variable is used to store the environment for the page like page attributes, access to the request, response and session objects. page: This variable is used to store the instance of the generated java servlet.
- 77. Scope of JSP ObjectsScope of JSP Objects The availability of a JSP object for use from a particular place of the application is defined as the scope of that JSP object. Every object created in a JSP page will have a scope. Object scope in JSP is segregated into four parts and they are page, request, session and application. page ‘page’ scope means, the JSP object can be accessed only from within the same page where it was created. The default scope for JSP objects created using <jsp:useBean> tag is page. JSP implicit objects out, exception, response, pageContext, config and page have ‘page’ scope. request A JSP object created using the ‘request’ scope can be accessed from any pages that serves that request. More than one page can serve a single request. The JSP object will be bound to the request object. Implicit object request has the ‘request’ scope.
- 78. session ‘session’ scope means, the JSP object is accessible from pages that belong to the same session from where it was created. The JSP object that is created using the session scope is bound to the session object. Implicit object session has the ‘session’ scope. application A JSP object created using the ‘application’ scope can be accessed from any pages across the application. The JSP object is bound to the application object. Implicit object application has the ‘application’ scope.