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Servlet 教程

Servlet 所有表单参数

以下是通用的实例，使用 HttpServletRequest 的 getParameterNames() 方法读取所有可用的表单参数。该方法返回一个枚举，其中包含未指定顺序的参数名。

一旦我们有一个枚举，我们可以以标准方式循环枚举，使用 hasMoreElements() 方法来确定何时停止，使用 nextElement() 方法来获取每个参数的名称。

实例

package com.runoops.test;

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;

/**
 * Servlet implementation class ReadParamsServlet
 */
@WebServlet("/ReadParamsServlet")
public class ReadParamsServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ReadParamsServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// 设置响应内容类型
        response.setContentType("text/html;charset=UTF-8");
        
        PrintWriter out = response.getWriter();
        String title = "读取所有的表单数据";
        String docType = "<!DOCTYPE html> \n";
            out.println(docType +
            "<html>\n" +
            "<head><meta charset=\"utf-8\"><title>" + title + "</title></head>\n" +
            "<body bgcolor=\"#f0f0f0\">\n" +
            "<h1 align=\"center\">" + title + "</h1>\n" +
            "<table width=\"100%\" border=\"1\" align=\"center\">\n" +
            "<tr bgcolor=\"#949494\">\n" +
            "<th>参数名称</th><th>参数值</th>\n"+
            "</tr>\n");

        Enumeration paramNames = request.getParameterNames();

        while(paramNames.hasMoreElements()) {
            String paramName = (String)paramNames.nextElement();
            out.print("<tr><td>" + paramName + "</td>\n");
            String[] paramValues =
            request.getParameterValues(paramName);
            // 读取单个值的数据
            if (paramValues.length == 1) {
                String paramValue = paramValues[0];
                if (paramValue.length() == 0)
                    out.println("<td><i>没有值</i></td>");
                else
                    out.println("<td>" + paramValue + "</td>");
            } else {
                // 读取多个值的数据
                out.println("<td><ul>");
                for(int i=0; i < paramValues.length; i++) {
                out.println("<li>" + paramValues[i]);
            }
                out.println("</ul></td>");
            }
            out.print("</tr>");
        }
        out.println("\n</table>\n</body></html>");
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

现在，通过下面的表单尝试上面的 Servlet：

实例

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>runoops 自学教程</title>
</head>
<body>

	<form action="ReadParamsServlet" method="POST" target="_blank">
		<input type="checkbox" name="maths" checked="checked" /> 数学 
		<input type="checkbox" name="physics" /> 物理 
		<input type="checkbox" name="chemistry" checked="checked" /> 化学 
		<input type="submit" value="选择站点" />
	</form>

</body>
</html>

现在使用上面的表单调用 Servlet，将产生以下结果：

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