Vishnu_VVV

 Eclipse Debugging ================= Debugging is a process of getting step by step by execution in an application to find out problem/bugs and fix them as needed. Terminologies associated with Debugging a. Bugs => Problem/defect/mistake in the app/program/project[some abnormality in the application execution] Debug = > De + bug [Rectifiying the bug by identifying and Analyzing the bug] The tools or programm or software that can be used for debugging is called "Debugger"/Debugging tool To debug java code we have two tools a. JDB(Supplied by jdk tools with jdk installation) => available inside <java_home>\bin directory as jdb.exe => it is CUI tool and not so popular(Not industry standard) b. IDE supplied Debugger => Eclipse/Intelij/EclipseLink and etc ... IDE supplied Debuggers => These are GUI and they are user friendly => These are industry standard Where Debugging is required in the company? a. To find,analyze and fix logic problems/errors b. if u...

  4 types of Specifiers/Modifiers 1. Public: Highest scope, will be accessed within the same class, outside class same package, outside package but child class, outside package no relation ship. 2. Protected: Next Highest scope, will be accessed within the same class, outside class same package, outside package but child class. 3 . Default: will be accessed within the same class, outside class same package. 4. Private: Least scope. will be accessed only within the same class UML( unified modeling language) Public -> + Protected -> # default -> ~ Private -> -

Technology is built on top of language where as framework is built on top of technology. 

 At the time of processing the later request, if we want to get the data of previous request, then we need to go for "session tracking." Every server side technology should support session tracking because the protocol used is http and it is 'stateless' in nature.

 This object is used to store the configuration details of a particular servlet like logical name of the servlet, initialization parameters and so on... Using servlet config we will get to know the complete view of a particular servlet. Servlet Config will be instantiated during the initialization of the Servlet.  Loading => static block  instantiation  => public zero arguments constructors  initialization => public void init (ServletConfig config) throws SE Request Processing => public void doXXXX(HSR request, HSR response) throws SE, IOE De Instantiation =>  public void destroy() Servlet Config object is specific to a particular servlet. Servlet Config object will be destroyed just before the Servlet Deinstantiation. We can add only parameters data inside the config object. In web.xml <init-params> will be placed under servlet class level as it is specific to particular servlet and the data present in one servlet config object cannot ...

 When we do deployment (manual), server will scan "webapps" folder and identifies the projects which is deployed.  All the identified projects will be kept in Meta-space of server. For every project which is deployed in 'Meta-space' automatically 'Servlet Context' object will be created.  Context object can be accessed in the entire project, meaning in all the servlets of the project. As this is the first object created after deployment. we can keep the database details like URL, username, password and we can retrieve when ever we required.   For all the servlets in the project what ever the data is required, that data will be placed in the Servlet Context object.  Servlet Context object will be destroyed when we undeployed the project. We can keep parameter data and attribute data inside the Servlet Context object. In web.xml, <context-params> will be placed under <web-app> because it will be accessible by all the servlets present in the projec...

 1. GET 2. POST 3. HEAD 4. PUT 5. DELETE 6. OPTIONS 7. TRACE GET, POST, HEAD are introduced in http protocol version 1.0v PUT, DELETE, OPTIONS, TRACE are introduced in http protocol version 1.0v GET and POST are used in web applications.