JSP nine large built-in objects

The JSP has the following 9 basic built-in components (which correspond to the 6 internal components of ASP):

FoldedRequest Object

The client's request information is encapsulated in the requests object to understand the customer's needs and respond. It is an instance of the HttpServletRequest class.

The request object has a requesting domain, which is valid until the client's request is completed.

Ordinal method Description

1 Object getattribute (String name) returns the property value of the specified property

2 enumeration Getattributenames () returns an enumeration of all available property names

3 String getcharacterencoding () returns the character encoding method

4 int Getcontentlength () returns the length of the request body (in bytes)

5 String getContentType () Gets the MIME type of the request body

6 ServletInputStream getInputStream () gets the binary stream of a row in the request body

7 string GetParameter (string name) returns the parameter value of name specified parameter

8 enumeration Getparameternames () returns an enumeration of the available parameter names

9 string[] Getparametervalues (String name) returns an array of all values that contain the parameter name

Ten String Getprotocol () returns the protocol type and version number of the request

One String Getscheme () returns the plan name of the request, such as: Http.https and FTP, etc.

String getServerName () returns the host name of the server that accepts the request

int Getserverport () returns the port number used by the server to accept this request

BufferedReader Getreader () returns the decoded request body

String getremoteaddr () returns the IP address of the client that sent this request

String Getremotehost () returns the host name of the client that sent this request

$ void SetAttribute (String key,object obj) to set property values for a property

Stringgetrealpath (String path) returns the true path of a virtual path

String Request.getcontextpath () returns the context path

FoldedResponse Object

The Response object contains information about the response to a customer request, but it is seldom used directly in the JSP. It is an instance of the HttpServletResponse class.

The response object has a page scope, that is, when a page is accessed, the response object within that page is valid only for this access, and the response object on the other page is not valid for the current page.

Ordinal method Description

1 String getcharacterencoding () returns what character encoding is used for the response

2 Servletoutputstream Getoutputstream () returns a binary output stream of the response

3 PrintWriter getwriter () returns an object that can output characters to the client

4 void setcontentlength (int len) Set response header length

5 void setContentType (String type) sets the MIME type of the response

6 Sendredirect (java.lang.String location) REDIRECT client request

FoldedSession Object

The session object refers to the client-to-server conversation, starting from the client connection to a webapplication of the server until the client disconnects from the server. It is an instance of the HttpSession class.

The session object is a JSP built-in object that is created automatically when the first JSP page is loaded, and completes conversation-period management. Open a browser from a client and connect to the server to start, to the client close the browser to leave the end of this server, known as a session. When a client accesses a server, it may switch between several pages of the server, and the server should know by some means that it is a client and needs a session object.

The session object has a conversation scope.

Ordinal method Description

1 long GetCreationTime () returns session creation time

2 public String GetId () returns the unique ID number that the JSP engine sets for the session when it is created

3 Long Getlastaccessedtime () returns the client's last request time in this session

4 int Getmaxinactiveinterval () returns two request interval how long this session was canceled (MS)

5 string[] GetValueNames () returns an array containing all the properties available in this session

6 void Invalidate () Cancel session to make session unavailable

7 Boolean isnew () returns a session created by the server, whether the client has joined

8 void RemoveValue (String name) removes the attribute specified in session

9 void Setmaxinactiveinterval () set two request interval how long this session is canceled (MS)

Soft Road Quotations

JSP built-in objects

A JSP built-in object is a Java class object that can be used in a JSP page.

FoldedOut Object

An Out object is an instance of the JspWriter class and is an object commonly used to output content to the client

Ordinal method Description

1 void Clear () clears the contents of the buffer

2 void Clearbuffer () clears the current contents of the buffer

3 void Flush () empty stream

4 int GetBufferSize () returns the buffer as the size of the number of bytes, or 0 if no buffer is set

5 int getremaining () returns how much of the buffer is remaining available

6 Boolean Isautoflush () returns when the buffer is full, automatically empties or throws an exception

7 void Close () close the output stream

FoldedPage Object

The Page object is pointing to the current JSP page itself, a bit like the this pointer in the class, which is an instance of the Java.lang.Object class

Ordinal method Description

1 class GetClass Returns the classes of this object

2 int hashcode () returns the hash code of this object

3 Boolean equals (Object obj) to determine whether this object is equal to the specified object objects

4 void Copy (object obj) copies this object to the specified object

5 Object Clone () to clone this object

6 string toString () converts this object to the object of the String class

7 void Notify () wakes up a waiting thread

8 void Notifyall () wakes up all waiting threads

9 void Wait (int timeout) causes a thread to wait until timeout ends or is awakened

Ten void Wait () causes a thread to wait until it wakes up

one void Entermonitor () lock on object

void Exitmonitor () to unlock object

FoldedApplication Object

The Application object implements the sharing of data among users and can store global variables. It starts at the start of the server until the server shuts down, during which time this object will persist, so that the same properties of the object can be manipulated on the user's back-and-forth connection or in a connection between different users, and the operation of this object property anywhere will affect access to it by other users. The startup and shutdown of the server determines the life of the Application object. It is an instance of the ServletContext class.

Ordinal method Description

1 Object getattribute (String name) returns the property value for the given name

2 enumeration Getattributenames () returns an enumeration of all available property names

3 void SetAttribute (String name,object obj) sets the property value of the property

4 void RemoveAttribute (String name) deletes an attribute and its property value

5 String Getserverinfo () returns the JSP (SERVLET) engine name and version number

6 string Getrealpath (string path) returns the true path of a virtual path

7 ServletContext getcontext (String uripath) returns the Application object for the specified WebApplication

8 int Getmajorversion () returns the maximum version number of the Servlet API supported by the server

9 int getminorversion () returns the minimum version number of the Servlet API supported by the server

Ten string GetMimeType (string file) returns the MIME type of the specified file

One-by-one URL getresource (String path) returns the URL path for the specified resource (file and directory)

InputStream getResourceAsStream (String path) returns the input stream for the specified resource

RequestDispatcher Getrequestdispatcher (String uripath) returns the RequestDispatcher object for the specified resource

Getservlet servlet (String name) returns the servlet of the specified name

Enumeration Getservlets () returns an enumeration of all Servlets

Enumeration Getservletnames () returns an enumeration of all servlet names

$ void log (String msg) writes the specified message to the servlet's log file

void log (Exception exception,string msg) writes the stack trace and error message of the specified exception to the servlet's log file

void log (String msg,throwable throwable) writes the description information of the stack trajectory and the given Throwable exception to the servlet's log file

FoldedException Object

The exception object is an exception object that is created when a page has an exception during the run. If a JSP page is to be applied to this object, the Iserrorpage must be set to true, otherwise it cannot be compiled. He's actually a java.lang.Throwable object.

Ordinal method Description

1 String getMessage () returns a message describing the exception

2 String toString () returns a short description message about the exception

3 void Printstacktrace () shows anomalies and their stack traces

4 throwable fillinstacktrace () Rewrite the exception's execution stack trajectory

FoldedPageContext Object

The PageContext object provides access to all objects and namespaces within the JSP page, which means that he can access the session where the page is located, or a property value of the application that is located on the pages, which is the equivalent of all the features in the page. Its class name is also called PageContext.

Ordinal method Description

1 JspWriter getout () returns the current client response used by the JspWriter stream (out)

2 HttpSession getsession () returns the HttpSession object (session) in the current page

3 Object GetPage () returns the current page of Object Objects (page)

4 ServletRequest Getrequest () returns the ServletRequest object of the current page (request)

5 Servletresponse GetResponse () returns the Servletresponse object of the current page (response)

6 Exception GetException () returns the Exception object of the current page (Exception)

7 ServletConfig Getservletconfig () returns the ServletConfig object (config) of the current page

8 ServletContext Getservletcontext () returns the ServletContext object of the current page (application)

9 void SetAttribute (String name,object attribute) set properties and property values

void SetAttribute (String name,object obj,int scope) sets properties and property values within a specified range

One public Object getattribute (String name) takes the value of the property

Object getattribute (String name,int scope) takes the value of the property within the specified range

Public Object Findattribute (String name) looks for a property that returns the property value or null

+ void RemoveAttribute (String name) to delete a property

void RemoveAttribute (String name,int scope) Deletes a property at the specified range

Getattributescope Int (String name) returns the scope of a property

Enumeration Getattributenamesinscope (int scope) Returns the property name enumeration available within the specified range

void release () releases the resources occupied by PageContext

Forward (String Relativeurlpath) to redirect the current page to another page

void include (String relativeurlpath) contains another file at the current location

FoldedConfig Object

The Config object is used by the JSP engine to pass information to it when a servlet is initialized, including the parameters to be used when the servlet initializes (through property names and property values) and information about the server (by passing a ServletContext object)

Ordinal method Description

1 ServletContext getservletcontext () returns ServletContext object containing information about the server

2 string Getinitparameter (string name) returns the value of the initialization parameter

3 enumeration Getinitparameternames () returns an enumeration of all parameters required by the servlet initialization

FoldedEdit the timing of the built-in objects in this paragraph

A JSP page corresponds to a servlet class with three methods per servlet class:

Init method: Initializes the Jsp/servlet method.

Destory method: Destroys the Jsp/servlet method.

Service method: The method that responds to a user request.

The request object and the response object are the parameters of the service method, the Application object, the Page object, the Out object, the PageContext object, and the session object are the instances generated in the service's method. These are described in more detail in struts ' self-media sites.

JSP nine large built-in objects