servlet3.0注解@WebInitParam和@WebServlet

转自：http://blog.csdn.net/qq924862077/article/details/52883973?locationNum=2&fps=1

在以前的servlet中我们初始化一些参数都是配置在web.xml中的，自从servlet3.0之后给我们提供了注解@WebServlet和@WebInitParam，@WebServlet是用来配置servlet的属性的，@WebInitParam是用来配置一些初始化属性的。

@WebServlet和@WebInitParam使用如下：

package roseindia.net;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;  

@WebServlet(
    name = "WebInitParamExample", urlPatterns = {"/hello"}
    ,initParams = {
    @WebInitParam(name= "Site :", value="http://roseindia.net"),
    @WebInitParam(name= "Rose", value= "India"),
    }
)
public class WebInitParamExample extends HttpServlet{
    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<h2>Init Param Servlet Example</h2>");
        ServletConfig config= getServletConfig();
        String pValue= config.getInitParameter("Site :");
        out.println("Param Value : "+pValue);
        String pValue1= config.getInitParameter("Rose");
        out.println("<br>Param Value : "+pValue1);
        out.close();
    }
}  

如果在web.xml中配置则如下：

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <display-name>servletAnnotationExample</display-name>
    <servlet>
        <servlet-name>WebInitParamExample</servlet-name>
        <servlet-class>roseindia.net.WebInitParamExample</servlet-class>
        <init-param>
            <param-name>Site :</param-name>
            <param-value>http://roseindia.net</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>WebInitParamExample</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>
</web-app>