ServletConfig:
A servlet configuration object used by a servlet container to pass information to a servlet during initialization.
Methods of ServletConfig:
A servlet configuration object used by a servlet container to pass information to a servlet during initialization.
Methods of ServletConfig:
Returns a String containing the value of the named initialization parameter, or null if the parameter does not exist.
java.util.Enumeration getInitParameterNames()
Returns the names of the servlet's initialization parameters as an Enumeration of String objects, or an empty Enumeration if the servlet has no initialization parameters.
ServletContext getServletContext()
Returns a reference to the ServletContext in which the caller is executing.
java.lang.String getServletName()
Returns the name of this servlet instance.
To get the ServletConfig Object
ServletConfig config = getServletConfig();
web.xml
Servlet_demo index.html simpleServlet com.jsl.servlets.SimpleServlet driver oracle.jdbc.driver.OracleDriver simpleServlet /simple
SimpleServlet.java
packagecom.jsl.servlets;
importjava.io.IOException;
importjava.io.PrintWriter;
importjavax.servlet.ServletConfig;
importjavax.servlet.ServletException;
importjavax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
publicclassSimpleServletextendsHttpServlet {
privatestaticfinallongserialVersionUID = 1L;
protectedvoiddoGet(HttpServletRequest request, HttpServletResponse response) throwsServletException, IOException {
ServletConfigconfig=getServletConfig();
response.setContentType("text/html");
PrintWriter out=response.getWriter();
out.print("<html><head><title>View Dept Details</head>");
out.print("<body>");
String driver=config.getInitParameter("driver");
out.print("
The Driver name is using servlet 3.0 :
"+driver);
out.print("</body>");
out.print("</html>");
}
protectedvoiddoPost(HttpServletRequest request, HttpServletResponse response) throwsServletException, IOException {
}
}
Servlet 3.0 the init parameters can be set by using the annotaions. we no need to configure in the web.xml
packagecom.jsl.servlets;
importjava.io.IOException;
importjava.io.PrintWriter;
importjavax.servlet.ServletConfig;
importjavax.servlet.ServletException;
importjavax.servlet.annotation.WebInitParam;
importjavax.servlet.annotation.WebServlet;
importjavax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
@WebServlet(
urlPatterns={"/simple"},
initParams={
@WebInitParam(name="driver",value="jdbc.oracle.driver.OracleDrvier")
}
)
publicclassSimpleServletextendsHttpServlet {
privatestaticfinallongserialVersionUID = 1L;
protectedvoiddoGet(HttpServletRequest request, HttpServletResponse response) throwsServletException, IOException {
ServletConfigconfig=getServletConfig();
response.setContentType("text/html");
PrintWriter out=response.getWriter();
out.print("<html><head><title>View Dept Details</head>");
out.print("<body>");
String driver=config.getInitParameter("driver");
out.print("
The Driver name is using servlet 3.0 :
"+driver);
out.print("</body>");
out.print("</html>");
}
protectedvoiddoPost(HttpServletRequest request, HttpServletResponse response) throwsServletException, IOException {
}
}
Servlet Context
public interface ServletContext
Defines a set of methods that a servlet uses to communicate with its servlet container, for example, to get the MIME type of a file, dispatch requests, or write to a log file.
There is one context per "web application" per Java Virtual Machine. (A "web application" is a collection of servlets and content installed under a specific subset of the server's URL namespace such as /catalog and possibly installed via a .war file.)
In the case of a web application marked "distributed" in its deployment descriptor, there will be one context instance for each virtual machine. In this situation, the context cannot be used as a location to share global information (because the information won't be truly global). Use an external resource like a database instead.
The ServletContext object is contained within the ServletConfig object, which the Web server provides the servlet when the servlet is initialized.
The context parameters can be set in the web.xml
<web-app>
<context-param>
<param-name>driver</param-name>
<param-value>oracle.jdbc.driver.OracleDriver</param-value>
</context-param>
</web-app>
To read this context-param
ServletContext context=getServletContext();
String dirver=context.getInitParam("driver");
Defines a set of methods that a servlet uses to communicate with its servlet container, for example, to get the MIME type of a file, dispatch requests, or write to a log file.
There is one context per "web application" per Java Virtual Machine. (A "web application" is a collection of servlets and content installed under a specific subset of the server's URL namespace such as /catalog and possibly installed via a .war file.)
In the case of a web application marked "distributed" in its deployment descriptor, there will be one context instance for each virtual machine. In this situation, the context cannot be used as a location to share global information (because the information won't be truly global). Use an external resource like a database instead.
The ServletContext object is contained within the ServletConfig object, which the Web server provides the servlet when the servlet is initialized.
The context parameters can be set in the web.xml
<web-app>
<context-param>
<param-name>driver</param-name>
<param-value>oracle.jdbc.driver.OracleDriver</param-value>
</context-param>
</web-app>
To read this context-param
ServletContext context=getServletContext();
String dirver=context.getInitParam("driver");
Diffrence Between the ServletConfig and ServletContext
ServletConfig
|
ServletContext
|
A servlet
configuration object used by a servlet container to pass information to a
servlet during initialization.
|
|
For each servlet
there will one ServletConfig object
|
The
entire web application will have one ServletContext Object
|
The parameters
specified in web.xml inside the <servlet> tag
|
The
paramemters are specified in web.xml inside <web-app>
|
These parameters
can be read by using config.getInitParameter(“name”);
|
These parameters
can be read by using context.getInitParameter(“name”);
|
No comments:
Post a Comment