HttpServlet 简单表单示例

本文代码转载自

《Servlet、JSP和Spring MVC初学指南》

下面是一个简单的利用get进行输入表单页面显示，post进行
表单提交内容展示的实例

package main.ServletTest;

/**
 * Created by ehang on 2017/2/8.
 */

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(
        name = "FormServlet",
        urlPatterns = {"/form"}
)
public class FormServlet extends HttpServlet {
    private static final long serialVersionUID = 54L;
    private static final String TITLE = "Order Form";

    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        writer.println("" +
                "
" +  TITLE + "
" +
                "
"
                + ""
                + ""
                + ""
                + ""
                + ""

                + ""
                + ""
                + ""
                + ""

                + ""
                + ""
                + ""
                + ""

                + ""
                + ""
                + ""
                + ""

                + ""
                + ""
                + ""
                + ""

                + ""
                + ""
                + ""
                + ""

                + ""
                + ""
                + ""
                + ""

                + ""
                + ""
                + ""
                + ""

                + "
Name:
Address:
Country:
"
                + "United States"
                + "Canada"
                + "
Delivery Method
First Class"
                + "Second Class"
                + "
Shipping Instructions:
"
                + "
 
Please send me the latest product catalog
 
"
                + "
" +
                "");
    }

    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response )throws ServletException, IOException{
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        writer.println("" +
                "" +
                "
" +
                TITLE +
                "
" +
                "" +

                "" +
                "" +
                "" +
                "" +

                "" +
                "" +
                "" +
                "" +

                "" +
                "" +
                "" +
                "" +

                "" +
                "" +
                "" +
                        "" +
                        "" +

                        "" +
                        "" +
                        "" +

                "
Name:
" +
                request.getParameter("name") +
                "
Address:
" +
                request.getParameter("address") +
                "
Country:
" +
                request.getParameter("country") +
                "
Shipping Instructions:
");

                String[] instructions = request.getParameterValues("instructions");
                if(instructions != null){
                    for(String instruction: instructions){
                        writer.println(instruction + "
");
                    }
                }

                writer.println("
Delivery Method:
" +
                        request.getParameter("deliveryMethod") +
                        "
Catalog Request:
");

                if(request.getParameter("catalogRequest") == null){
                    writer.println("No");
                }
                else{
                    writer.println("Yes");
                }
                 writer.println( "
");

                writer.println(
                "
" +
                        "Debug Info
");

                Enumeration parameterNames = request.getParameterNames();
                while(parameterNames.hasMoreElements()){
                    String paramName = parameterNames.nextElement();
                    writer.println(paramName + ": ");
                    String[] paramValues = request.getParameterValues(paramName);
                    for(String paramValue: paramValues){
                        writer.println(paramValue + "
");
                    }
                }

                writer.println(
                "
" +
                "");

    }

}

使用input标签对应的name来通过request.getParameter得到提交值。

该例使用 annotation WebServlet urlPatterns映射，一般提到的映射方式为web.xml中的部署描述符配置方式。
后者较前者的优势在于提供了WebServlet所不支持的若干描述 如位于中可配置
该节点支持整数值作为输入，指定在程序启动时而非第一次调用时初始化servlet类，
当对多个servlet都配置了该节点时，不同的load-on-start节点值决定了载入的先后顺序，
基本上类似于对中间件指定载入顺序。
描述符配置的方式也可包含如servlet进行初始化信息。

如利用annotation WebServlet可如下指定servlet初始化参数

@WebServlet(
    name = "test",
    urlpatterns = {"/test"};
    initParams = {
        @WebInitParams(name = "admin", value = "SV")
    }
)

相应的部署描述符servlet配置为

    test
    SomeClass
    
        admin
        SV
    



    test
    /test