JSP-9 large built-in objects and their APIs

Built-in objects: You can use them in script code and expressions without having to declare them in advance, with the following characteristics

1. Provided by the JSP specification without being instantiated by the creator

2. Provide Web container implementation and management

3. All JSP pages are available

4. Can be used only in expressions or code in script elements (<%= using built-in object%> or <% using built-in object%>)

Input and Output object: Request,response,out

Communication Control object: Pagecontext,session,application

Servlet object: Page,config

Error Handling object: exception

1. Request-Object Javax.servlet.httpServletRequest

The request object is an instance of the Javax.servlet.httpServletRequest class that represents the client's requested information and is primarily used to accept data that is delivered to the server over the HTTP protocol. (including header information, System Information, request method, request parameters, etc.).

The request object is scoped to the requested one time, and when the request is sent, the object is created and destroyed once the request is completed (one request, resulting in a requester object)

The object encapsulates the user-submitted information by invoking the corresponding method of the object to obtain the encapsulated information, which can be used to obtain the user-submitted information.

1 string getparameter (string name) returns the parameter value of name specified parameter

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

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

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

5 Object GetAttribute (String name) returns the property value of the specified property (that is, the value of the parameter key in setattribute)

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

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

8 String getServerName () returns the server accepting the request?

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

Ten BufferedReader Getreader () returns the decoded request body

One String getremoteaddr () returns the IP address of the client sending this request

String Getremotehost () returns the client sending this request?

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

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

String getcharacterencoding () returns the character encoding method

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

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

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

2. Response-Response Object Javax.servlet.http.HttpServletResponse

Response represents the response to the client, primarily by returning the objects processed by the JSP container back to the client

Dynamic response to client requests, sending data to the client, setting up in response to client requests, destroying at end of response (one response, producing a response object)

Dynamic Response ContentType Properties:

When a user accesses a JSP page, the JSP engine responds to this property value if it sets the page's ContentType property to text/html with the page directive. If you want to dynamically change this property value in response to the customer, you need to use the response object

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

3. Session-Conversation Object javax.servlet.http.HttpSession

Created in the page instruction by adding session= "true" or by default and using Request.getsession () in the servlet. The session ends when the timeout or service is stopped. (one user corresponds to a Session object)

What is a Session object? --it is a JSP built-in object that is created automatically when the first JSP is loaded, completing session-period management. Opening a browser from a client and connecting to the server begins with the client closing the browser and leaving the server end (or timeout), known as a session. When a client accesses a server, it is possible to switch between several pages of the server, and the server should know that it is a customer and need to create a Session object

id--of Session object when a client accesses a JSP page on the server for the first time, the JSP engine generates a session object, assigning a string ID number, and the JSP engine sends the ID number to the client, which is stored in a cookie, so , the session object will not disappear until the client closes the browser, and the client's conversational counterpart disappears. When the customer re-opens the browser and then connects to the server, the server creates a new session object for the customer

1 long GetCreationTime () returns session creation time

2 public String GetId () returns the unique ID number that the JSP engine assigns to 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)

4. Application-Application Object Javax.servlet.ServletContext

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

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 maximum 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

5. Out-Data Flow object Javax.servlet.jsp.jspWriter

An Out object is an instance of the Javax.servlet.jsp.JspWriter class that is used to write content to the response object and output to the page

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

6. PageContext-Page Context object Javax.servlet.jsp.PageContext

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. The name of this class is also called PageContext

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

7.config-Configuration Object Javax.servlet.ServletConfig

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)

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

8. Page-Current JSP Page Object java.lang.object

The Page object is a pointer to the current JSP page itself, similar to the This keyword in the class, where the object is a reference to the page instance. It can be seen as a representation of the entire JSP page, which is an instance of the Java.lang.Object class

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 object*

9. Exception-Exception Object java.lang.Throwable

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. It's the object of Java.lang.Throwable.

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

JSP-9 large built-in objects and their APIs