[Original]java Web learning Note 06:servletcontext interface

this blog is original: Integrated still Silicon Valley (http://www.atguigu.com) System tutorial (deep thank) and network of existing resources (blogs, documents, books, etc.), the source of resources I will markThe purpose of this blog: ① summary of their own learning process, equivalent to study notes ② to share their own experience to everyone, learn from each other, communication, not commercialcontent inevitably appear problems, welcome to correct, exchange, discussion, you can leave a message, can also be contacted by the following ways. I Internet technology enthusiasts, Internet technology enthusiastsWeibo: Ivan is in 0221qq:951226918

--------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------- -----------------------------

1. About Servletcontex

1) The servlet engine creates a corresponding ServletContext object for each Web application, and the ServletContext object is contained in ServletConfig (about ServletConfig reference another blog) object, call the Servletconfig.getservletcontext method to return a reference to the ServletContext object .

2) because all servlets in a Web application share the same ServletContext object , the ServletContext object is called a Application object (Web Application object); is important

3) functions that can be implemented (get information on various aspects of the current application)

> Get initialization parameters for a Web application

> Logging

>application Domain-wide properties

> Accessing resource Files

> Get the local path mapped by the virtual path

>web Access between applications

2. Configure ServletContext: In the current web directory of the XML configuration, each configuration of a parameter, you must re-create a <context-param> </context-param> node, after configuration is complete, the initialization parameters for Servletcontex can be obtained for any servlet. Two servlet initialization parameters, only the current servlet can get

1     <!--Configure initialization parameters for the current WEB app -2     <Context-param>3         <Param-name>Driver</Param-name>4         <Param-value>Com.mysql.jdbc.Driver</Param-value>5     </Context-param>6     7     <Context-param>8         <Param-name>Jdbcurl</Param-name>9         <Param-value>Jdbc:mysql:///test</Param-value>Ten     </Context-param>

3. Get configuration information for ServletContext

1) getinitparameter (String parametername): Gets the parameter value of the initialization driver

2) getinitparameternames () : Gets all the parametername values

3) Getrealpath (String path): Gets the absolute path of one of the currently applied files on the server , must be under the WebContent folder

4) Getcontexpath (): Gets the name of the current app  

5) getResourceAsStream (String path) path/is the root directory relative to the Web App : Gets the input stream for a file of the current WEB app (very important), Create a jdbc.properties under SRC

1 @Override2      Public voidInit (ServletConfig servletconfig)throwsservletexception {3System.out.println ("Init");4 5         //1. Get the ServletContext object, the current web app information6ServletContext ServletContext =Servletconfig.getservletcontext ();7 8         //2. Get the parameter values for initializing driver9String Driver = servletcontext.getinitparameter ("Driver");TenSystem.out.println ("Driver:" + driver);//output-Driver One                                                 //: Com.mysql.jdbc.Driver A  -         //3. Get all parametername values, output -enumeration<string> names =servletcontext.getinitparameternames (); the          while(Names.hasmoreelements ()) { -String name =names.nextelement (); -SYSTEM.OUT.PRINTLN (name);//output, driver Jdbcurl -         } +  -         //4. Obtain an absolute path to a file on the server that is currently applied and must be in the WebContent folder +String Realpath = Servletcontext.getrealpath ("/hello.jsp"); A         //Output at         //E:\java_workspase\eclipes\.metadata\.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps\javaWEB\ hello.jsp - System.out.println (realpath); -  -         //5. Get the name of the current app -String ContextPath =Servletcontext.getcontextpath (); -System.out.println (ContextPath);//Output-/javaweb in  -         //gets the input stream for a file of the current web App to         //Way One: +         Try { -ClassLoader ClassLoader =getclass (). getClassLoader (); theInputStream is = Classloader.getresourceasstream ("Jdbc.properties"); *System.out.println ("1." +is ); $}Catch(Exception e) {Panax Notoginseng e.printstacktrace (); -         } the  +         //Way Two: A         Try { the             //The path is the absolute path to the Web project in the server, where/is the root: that is, the webcontent in development +InputStream Is2 =ServletContext -. getResourceAsStream ("/web-inf/classes/jdbc.properties"); $System.out.println ("2." +is2); $}Catch(Exception e) { -  - e.printstacktrace (); the         } - Wuyi}

4. Summary

1) fully understand the ServletContext object: Represents the entire Web application

2) Understand each method

[Original]java Web learning Note 06:servletcontext interface