获取web.xml文件中的信息

key
value

servletContext.getInitParameter(“key”)
该方法可以读取web.xml文件中标签中的配置信息。
servletContext.getInitParameterNames()
该方法可以读取web.xml文件中所有param-name标签中的值。

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
public class ContextReadInfoServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        Enumeration<String> initParameterNames = servletContext.getInitParameterNames();
        PrintWriter printWriter = resp.getWriter();
        while (initParameterNames.hasMoreElements()){
            String name = initParameterNames.nextElement();
            String value = servletContext.getInitParameter(name);
            printWriter.println(value);
        }
        printWriter.flush();
        printWriter.close();
    }
}