Term
Describe an http request. |
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Definition
An http client sends an http request to a server in the form of a request message.
Request line
request method
request uri
request header fields |
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Term
| List the HTTP request methods |
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Definition
get
head
post
put
delete
connect
options
trace |
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Term
| Describe header request fiels |
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Definition
| the header request fields allow the client ot pass additional information about hte request and about hte client itself to the server. |
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Term
| Give simple example of request message |
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Definition
GET /hello.htm HTTP/1.1
User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT)
Host: www.tutorialspoint.com
Accept-Language: en-us
Accept-Encoding: gzip, deflate
Connection: Keep-Alive |
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Term
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Definition
A uniform resource identifier is a case-sensative string containing name, location, etc to identify a resource.
syntax: URI = "http:" "//" host [ ":" port ] [ abs_path [ "?" query ]]
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Term
| What is the http date/time stape format? |
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Definition
| Greenwich mean time, no exceptions |
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Term
| What is the default character set? |
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Definition
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Term
| What is a content enconding? |
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Definition
content encoding value indicates that an encoding algorithm has been used to encode the content before passing it over to the network.
Accept-encoding: gzip
or
Accept-encoding: compress
or
Accept-encoding: deflate |
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Term
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Definition
http uses language tags within the accept-language and content-language fields. A language tag is composed of one or more parts: a primary langauge tag and possibly empty series of subtags.
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Term
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Definition
| an http client is a program (web browser) that establishes a connection to a server for the purpose of sending one or more http request messages. |
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Term
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Definition
| an http server is a program that accepts connections in order to serve http requests by sending http response messages. |
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Term
| What is an http message start line |
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Definition
A start-line will have the following generic syntax:
start-line = Request-Line | Status-Line
We will discuss Request-Line and Status-Line while discussing HTTP Request and HTTP Response messages respectively. For now, let's see the examples of start line in case of request and response:
GET /hello.htm HTTP/1.1 (This is Request-Line sent by the client)
HTTP/1.1 200 OK (This is Status-Line sent by the server) |
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Term
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Definition
http header fields provide required information about the reuqest or response or about the object sent in the message body
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Term
| What are the 4 types of http message headers? |
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Definition
-
General-header: These header fields have general applicability for both request and response messages.
-
Request-header: These header fields have applicability only for request messages.
-
Response-header: These header fields have applicability only for response messages.
-
Entity-header: These header fields define meta information about the entity-body or, if no body is present, about the resource identified by the request.
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Term
| what is the message body of an http message? |
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Definition
A message body is the one which carries the actual HTTP request data (including form data and uploaded, etc.) and HTTP response data from the server ( including files, images, etc.). Shown below is the simple content of a message body:
<html>
<body>
<h1>Hello, World!</h1>
</body>
</html> |
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Term
| What is an http response? |
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Definition
After receiving and interpreting a request message, a server responds with an HTTP response message:
- A Status-line
- Zero or more header (General|Response|Entity) fields followed by CRLF
- An empty line (i.e., a line with nothing preceding the CRLF) indicating the end of the header fields
- Optionally a message-body
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Term
| what are the parts of an http response |
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Definition
Message status line
http version
status code
response header fields
HTTP/1.1 200 OK
Date: Mon, 27 Jul 2009 12:28:53 GMT
Server: Apache/2.2.14 (Win32)
Last-Modified: Wed, 22 Jul 2009 19:15:56 GMT
Content-Length: 88
Content-Type: text/html
Connection: Closed |
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Term
| What are the http methods? |
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Definition
get
head
post
put
delete
connect
options
trace |
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Term
| What does the get method do? |
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Definition
| A GET request retrieves data from a web server by specifying parameters in the URL portion of the request. This is the main method used for document retrieval. |
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Term
| What does the post method do? |
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Definition
| The POST method is used when you want to send some data to the server, for example, file update, form data, etc. |
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Term
| What are the 5 http status codes? |
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Definition
| S.N. |
Code and Description |
| 1 |
1xx: Informational
It means the request has been received and the process is continuing.
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| 2 |
2xx: Success
It means the action was successfully received, understood, and accepted.
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| 3 |
3xx: Redirection
It means further action must be taken in order to complete the request.
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| 4 |
4xx: Client Error
It means the request contains incorrect syntax or cannot be fulfilled.
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| 5 |
5xx: Server Error
It means the server failed to fulfill an apparently valid request.
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Term
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Definition
| HTTP URLs can only be sent over the Internet using the ASCII character-set, which often contain characters outside the ASCII set. So these unsafe characters must be replaced with a %followed by two hexadecimal digits. |
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Term
| What is the difference between URI AND URL |
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Definition
URIs identify and URLs locate; however, locators are also identifiers, so every URL is also a URI, but there are URIs which are not URLs.
uniform resource locator
uniform resource identifier |
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Term
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Definition
A servlet is a small Java program that runs within a Web server. Servlets receive and respond to requests from Web clients, usually across HTTP, the HyperText Transfer Protocol.
A servlet is an interface in java.
it is implemented by GenericServlet.
Defines methods that all servlets must have.
This interface defines methods to initialize a servlet, to service requests, and to remove a servlet from the server. These are known as life-cycle methods and are called in the following sequence:
- The servlet is constructed, then initialized with the
init method.
- Any calls from clients to the
service method are handled.
- The servlet is taken out of service, then destroyed with the
destroy method, then garbage collected and finalized.
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Term
what is the genericservlet class?
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Definition
Defines a generic, protocol-independent servlet. To write an HTTP servlet for use on the Web, extend HttpServlet instead.
GenericServlet implements the Servlet and ServletConfig interfaces. GenericServlet may be directly extended by a servlet, although it's more common to extend a protocol-specific subclass such as HttpServlet.
GenericServlet makes writing servlets easier. It provides simple versions of the lifecycle methods init and destroy and of the methods in the ServletConfig interface. GenericServlet also implements the log method, declared in the ServletContext interface.
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Term
| What is the httpservlet class? |
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Definition
- public abstract class HttpServlet
- extends GenericServlet
- implements java.io.Serializable
Provides an abstract class to be subclassed to create an HTTP servlet suitable for a Web site. A subclass of HttpServlet must override at least one method, usually one of these:
doGet, if the servlet supports HTTP GET requestsdoPost, for HTTP POST requestsdoPut, for HTTP PUT requestsdoDelete, for HTTP DELETE requestsinit and destroy, to manage resources that are held for the life of the servletgetServletInfo, which the servlet uses to provide information about itself
There's almost no reason to override the service method. service handles standard HTTP requests by dispatching them to the handler methods for each HTTP request type (the doXXX methods listed above).
Likewise, there's almost no reason to override the doOptions and doTrace methods. |
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Term
| What is the inheritance tree of a servlet? |
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Definition
Servlet interface
GenericServlet
HttpServlet (abstract)
MyServlet (implements abstract methods) |
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Term
| Why are there no constructors in servlets? |
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Definition
| A servlet is just like an applet in the respect that it has an init() method that acts as a constrcutor. Since the servlet environment takes care of instantiating the servlet, an explicit constructor is not needed. Any initialization code you need to run should be placed in the init() method since it gets called when the servlet is first loaded by the servlet container. |
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Term
What is the difference between GenericServlet and HttpServlet? |
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Definition
GenericServlet is a class.
HttpServlet is an abstract class.
HTTPServlet is for http responses.
Generic Servlet would be used for FTP and other protocols. |
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Term
What is the difference between the doGet and doPost methods? |
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Definition
doGet is called in response to an HTTP GET request. This happens when users click on a link, or enter a URL into the browser’s address bar. It also happens with some HTML FORMs (those with METHOD=”GET” specified in the FORM tag).
doPost is called in response to an HTTP POST request. This happens with some HTML FORMs (those with METHOD=”POST” specified in the FORM tag).
Both methods are called by the default (superclass) implementation of service in the HttpServlet base class. You should override one or both to perform your servlet’s actions. You probably shouldn’t override service(). |
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Term
What is meant by the term “business logic”? |
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Definition
| More precisely, in a three-tier architecture, business logic is any code that is not specifically related to storing and retrieving data (that’s “data storage code”), or to formatting data for display to the user (that’s “presentation logic”). |
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Term
How can I explicitly unload a servlet or call the destroy method? |
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Definition
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Term
What is a web application (or “webapp”)? |
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Definition
| A web application is a collection of servlets, html pages, classes, and other resources that can be bundled and run on multiple containers from multiple vendors. A web application is rooted at a specific path within a web server. |
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Term
What is a Servlet Context? |
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Definition
| A Servlet Context is a grouping under which related servlets (and JSPs and other web resources) run. They can share data, URL namespace, and other resources. There can be multiple contexts in a single servlet container. |
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Term
What are the different cases for using sendRedirect() vs. getRequestDispatcher()? |
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Definition
| When you want to preserve the current request/response objects and transfer them to another resource WITHIN the context, you must use getRequestDispatcher or getNamedDispatcher. |
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Term
| What is the lifecyle of a servlet? |
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Definition
init()--used as a constructor
service() --where we override doGet
destroy() no control. |
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Term
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Definition
Servlet mapping occurs in the web.xml file and as an annotation.
in the xml file, there are 4 or 5 lines.
<servlet-name>
<servlet-class>
<load on startup> optional
<servlet-mapping>
<servlet-name>
<url-pattern> |
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Term
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Definition
JavaScript, often abbreviated as JS, is a high-level, dynamic, weakly typed, prototype-based, multi-paradigm, and interpreted programming language. Alongside HTML and CSS, JavaScript is one of the three core technologies of World Wide Web content production.
it is used to manipulate the DOM. |
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Term
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Definition
ajax stands for asynchronous javascript and xml.
it means it's non-blocking
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Term
| What are the components of an ajax request? |
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Definition
var request = new XMLHttpRequest();
request.onreadystatechange = function () {
var DONE = this.DONE || 4;
if (this.readyState === DONE){
alert(this.readyState);
}
};
request.open('GET', 'somepage.xml', true);
//request type, url, aynchronous is true
request.setRequestHeader('X-Requested-With', 'XMLHttpRequest'); |
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Term
|
Definition
Document object model.
The Document Object Model (DOM) is a cross-platform and language-independent application programming interface that treats a HTML, XHTML, or XML document as a tree structure wherein each node is an object representing a part of the document. The objects can be manipulated programmatically and any visible changes occurring as a result may then be reflected in the display of the document.The Document Object Model (DOM) is a cross-platform and language-independent application programming interface that treats a HTML, XHTML, or XML document as a tree structure wherein each node is an object representing a part of the document. The objects can be manipulated programmatically and any visible changes occurring as a result may then be reflected in the display of the document. |
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Term
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Definition
javascript object notation
common format
human readable
key value pairs |
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Term
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Definition
data about data.
pom.xml
web.xml |
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Term
| What si the difference between form and javascript? |
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Definition
form is synchronous
javascript is asynchronous. |
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Term
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Definition
Maven is a project management and comprehension tool.
Maven provides developers a complete build lifecycle framework. Development team can automate the project's build infrastructure in almost no time as Maven uses a standard directory layout and a default build lifecycle. |
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Term
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Definition
POM stands for project oject model.
it is the fundamental unit of work in maven.
it's an xml file.
contains information to build the file along with configuratoin details. |
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Term
| What are the elements of a project's coordinates? |
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Definition
<groupId>
<artifactId>
<version> |
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Term
| What are the different maven build lifecycles? |
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Definition
|
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Term
| What are the phases of the default lifecycle? |
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Definition
| validate, compile, test, package, integration-test, verify, install,deploy |
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Term
| what would the command mvn clean do? |
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Definition
| this command removes the target directory with all the build data before starting the build process. |
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Term
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Definition
| a goal represents a specific task which contributes to hte building and managing of a project. |
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Term
|
Definition
| archtype is a maven pligin whose task is to create a project structure as per its template |
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Term
|
Definition
a dependency is an artifact that maven will include as part of hte build.
it's like including a jar file in your classpath |
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Term
What is a maven repository?
what are the local and central repositories? |
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Definition
a maven repository is a directory where all the project jars, libraries, plugins or any other project artifacts are stored and can be easily used by maven.
maven has a local repository and a remote.
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Term
| What is the default location of your local repository? |
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Definition
|
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Term
| how do you deploy a web applicatoin using maven? |
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Definition
using the appropriate maven plugin such as weblogic-maven-plug or tomcat-maven - plugin
the plugin info must be included in the pom file
then exceute the goal assicated with the maven plugin.
mvn weblogic:deploy |
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Term
|
Definition
snapshot is a special version that indicates a current development copy.
unlike regular version, maven checks for a new snapshot version in a remote repository for every build. |
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Term
| how do you install a jar file to your local repository? |
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Definition
| mvn install: install-file -dfile = path -dgroupid=com.example -datrifactid = artifact -dversion =1.0.0 -dpacking=jar |
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Term
| what is hte command to create a new project based on an archtype? |
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Definition
| mvn archetype:generate -dgroupid=yourproject's group id -dartifactid=yourprojects' artifact id -darchetypeartifactid = maven-archtye-archetype |
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Term
| in what order does maven resolve dependencies? |
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Definition
search for dependencies in local .m2
sarch for dependencies in central repository
if remote repo
search for depencies in remote repo
if no remote repo
stop processing and error
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Term
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Definition
| a connection pool contains a group of jdbc connection that are created when the connection pool is registered. |
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Term
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Definition
oracle creates a memmory area known as context area for processing a sql statement.
a cursor is a pointer to this context area. |
|
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Term
| what is an impllicit cursor? |
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Definition
| implicit cursors are automatically created by oracle whenever an sql statement is executed, when there is no explcicit cursor fot he statemnt |
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Term
| what is an explicit cursor? |
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Definition
| explciity cursors are programmer defined cursors for gaining more control over the context area |
|
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Term
|
Definition
oracle creates a memmory area known as context area for processing a sql statement.
a cursor is a pointer to this context area. |
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Term
| What is an implicit cursor? |
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Definition
| implicit cursors are automatically created by oracle whenever a sql statement is executed when there is no explicit cursor for the statement. |
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Term
| what is an explicit cursor? |
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Definition
| explicit cursors are programmer defined cursors for gaining more control over the context area. |
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|
Term
| what is amazon ec2 service? |
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Definition
ec2 use xen virtualization
it allows you to launch virtual machines that scale accroding to your needs |
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Term
| what is the relation between ec2 instance and ami? |
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Definition
| we can launch different types of instances from a single AMI. |
|
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Term
| what is amazon machine image? |
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Definition
| an amazon machine image is a template that contains a software configuration (OS).from ami we can launch an instance, which is a copy of the ami running as a virtual server |
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Term
| explain storage for amazon ec2 instance |
|
Definition
amazon provides many data storage options for your isntances.
each option has a unique combination of performance and durability.
these storage options can be used independently or in combination to suit your requirements
there are 4 types
Amazon EBS
Amazon EC2 intance store
Amazon S3
Adding storage |
|
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Term
|
Definition
Elastic block store is a durable, block-level storage volume that you can attach to a running amazon ec2 instance. the EBS persists independently from the EC2.
after attached to an ec2 it can be used like a physical hdd. |
|
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Term
| what is amazon ec2 instance store? |
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Definition
| storage disk that is attached to the host computer is referreed to as an instance store. instances storage provides temporary blcock-level storage for amazon ec2 instances. |
|
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Term
|
Definition
| amazon route 53 is a highly available and scalable cloud domain name seystem web service |
|
|
Term
| what is amazon elastic load balancing? |
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Definition
| Elastic load balancing automatically distrubtes incoming app traffic across multiple amazon ec2 instances in the cloud. |
|
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Term
| what are regions and availability zones? |
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Definition
the aws cloud infrastructure is built around regions and availability zones.
A region is a physical location which has multiple availability zones.
Availability zones consists of one ore more discrete data centers |
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Term
| what is a key pair?explain how to create a key pair. |
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Definition
EC2 uses pulbic key cryptography to encrypt and ecrypt login information. public key cryptography uses a pulbic key to encrypt a piece of data such as a password and then the recipeiint uses the private key to decrypt the data. these keys are the key pair.
to login to an ec2 you must create a key pair.
windows: key pair to get admin password.
linux: uses key pair to login using ssh |
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Term
| what is a security group in amazon ec2? what are the features of security group in amazon ec2? |
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Definition
| a security group acts as a virtual firewall that controls the traffic for one or more instances. |
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Term
| how to connect to your amazon ec2 instance? |
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Definition
you connect to a linux ec2 using ssh or putty.
you connect to windows using remote desktop |
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Term
| how are you charged in amazon ec2? |
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Definition
| aws allows you to pay for servces on demand and to use as much or as little at any given time as you need. |
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Term
| can i vertically scan an ec2 instance? |
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Definition
| yes. you can start a new larger instance than what you started with . pause, detach ebs stop live isntance. detach its root volume, attach new root volume to server and then start again. |
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Term
| What is auto-scaling how does it work? |
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Definition
| autoscaling is a feature of aws which allows you to configure and automatically provision and spinup new instances without the need for your intervention. you configure a threshold to launch a new isntance. |
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Term
| what automation tools cna i use to spinup servers? |
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Definition
the most obvious way to is to roll your own scripts and use the aws api tools.
script->use config management and provision tool. |
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Term
| what is configuration management and why would i want to use it with cloud provisioning of resources? |
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Definition
configuration management brings a large automation tool into the picture managing servers like strings of a puppet.
this forces tandarization, best practices and reproducibility as all configs are versioned and managed. |
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Term
| what is the difference between scalability and elasticity? |
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Definition
scalability is a characteristic of cloud ocmputing through which increasing workload can be handled by increasing in proportion and the amount of resource capacity
elasticity is being one of hte characteristics provides the concept of commisioning and decommisioning of large amount of resource capacity dynamically. it is measured by the speed by which resources are coming on demand and the usage of those resources. |
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Term
| what are the different layers of cloud computing? |
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Definition
infrastructure as a service (hardware)
platform a sa service (cloud app platform for devs)
software as a service (privdes cloud apps which are use directly) |
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Term
| how do you use amazon sqs? |
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Definition
| amazon simple queue service is a fast reliable managed message queing services. |
|
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Term
| how buffer is used in AWS? |
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Definition
| buffer is ued to make the system more resilient to burst ortraffic or load by synchronizing different components . |
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Term
| what are security best practices for EC2? |
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Definition
restric acess by only allowing trusted hosts or networks.
review the rules in your security group regularly.
only open up permissions you require.
disable password based logins for isntances launched from ami. |
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