JSP Implicit Objects

1. JSP Implicit Objects CS 422 Dick Steflik

2. Implicit Objects • Objects created by the servlet container • application • session • request • response • exception • out • Config • pageContext • page

3. Application Object • Used to share data between all of the pages that make up an application • All users share the Application Object • Can be accessed from any JSP in the application via the ServletContext • javax.servlet.http.ServletContext

4. Application Object Methods • getAttribute(String name) • getAttributeNames • setAttribute(String objName, Object object) • removeAttribute(String objName) • getMajorVersion() • getMinorVersion() • getServerInfo() • getInitParameter(String name) • getInitParameterNames • getResourceAsStream(Path) • log(Message)

5. Sessions • A session is a concept that represents a series of HTTP requests and responses between a specific browser and a specific server. • Sessions are managed by the server • Created by the server when the first request is received from a browser on a new host the server starts the session and assigns it an ID. • The ID is sent to the browser as a cookie and remembered by the server

6. Sessions (more) • The server creates a Session object that contains the attributes: • Creation Time • ID • Last Time Accessed • Maximum Inactive Time allowed

7. HTTPSession Interface • getAttribute() – returns the object associated with the specified key string • getAttributeNames() – returns an enumeration of the key strings in the session • getCreationTime() – returns the time the session was created; millsecs past midnight since Jan 1, 1970 GMT • getID() – returns the session ID as a string • getLastAccessedTime() – returns thelast time the client sent a request for this session • getMaxInactiveInterval() – returns the maximun amount of time that the servlet container between client requests before timing out the session • setAttribute() – associates an object with a key string in the session • removeAttribute() – remove an attribute from the session • setMaxInactiveInterval() – set the time in seconds allowed between client requests • isNew() – true if a new session, false otherwise

8. request Object • Javax.servlet. http.httpservletrequest. • The object request is of type Javax.servlet.http.httpservletrequest. • This denotes the data included with the HTTP Request. • The client makes a request that is then passed to the server. • The requested object is used to take the value from client’s web browser and pass it to the server. • This is performed using HTTP request like headers, cookies and arguments.

9. response Object • Javax.servlet.http.HttpServletResponse • The HTTP Response data. • The result or the information that fulfills an Http request • The object response is of type javax.servlet.http. >httpservletresponse. Generally, the object response is used with cookies. The response object is used to build the HTTP response header

10. pageContext Object • Javax.servlet.jsp.pagecontext • Used to access page attributes and also to access all the namespaces associated with a JSP page.

11. Out Object • The Output stream in the context of page. • The class or the interface name of the Out object is jsp.JspWriter. • The Out object is written: Javax.servlet.jsp.JspWriter

12. config Object • This is used to get information regarding the Servlet configuration • The class or the interface name of the Config object is ServletConfig. • The object Config is written Javax.servlet.http.ServletConfig

13. page Object • The Page object denotes the JSP page • Used for calling any instance of a Page's servlet. • The class or the interface name of the Page object is jsp.HttpJspPage. • The Page object is written: Java.lang.Object

14. Passing Values from Page to Page • Put values in the session object • Put the values in the application object • Put values at the end of the URL