入门servlet：request获取请求参数通用方式

一、获取请求参数通用方式

1.　String getParameter(String name)：根据参数名称获取参数值　例：username=flypig&password=2343

2.　String[] getParameterValues(String name)：根据参数名称获取参数值的数组　　例：hooby=xx&hobby=name

3.　Enumeration<String> getParameterNames()：获取所有请求的参数名称

4.　Map<String, String[]> getParameterMap()：获取所有参数的map集合

@WebServlet("/RequestDemo6")
public class RequestDemo6 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //post 获取请求参数

        //根据参数名称获取参数值
        String username = request.getParameter("username");
//        System.out.println("post");
//        System.out.println(username);

        //根据参数名称获取参数值的数组
        String[] hobbies = request.getParameterValues("hobby");
//        for (String hobby : hobbies) {
//            System.out.println(hobby);
//        }

        //获取所有请求的参数名称

        Enumeration<String> parameterNames = request.getParameterNames();
//        while(parameterNames.hasMoreElements()){
//            String name = parameterNames.nextElement();
//            System.out.print(name+":");
//            String value = request.getParameter(name);
//            System.out.println(value);
//        }

        //获取所有参数的map集合
        Map<String, String[]> parameterMap = request.getParameterMap();
        //遍历
        Set<String> keySet = parameterMap.keySet();
        for (String name : keySet){

            //根据键获取值
            String[] values = parameterMap.get(name);
            System.out.println(name);
            for (String value : values) {
                System.out.println(value);
            }
            System.out.println("--------------");
        }


    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get获取请求参数

        //根据参数名称获取参数值
//        String username = request.getParameter("username");
//        System.out.println("get");
//        System.out.println(username);

        this.doPost(request,response);
    }
}

二、解决乱码问题

解决请求参数中文乱码问题：

　　* get方式：tomcat 8已经将get方式乱码问题解决

　　* post方式：会乱码

　　　　*解决：在获取参数前，设置request的编码request.setCharacterEncoding("utf-8")

@WebServlet("/RequestDemo7")
public class RequestDemo7 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //设置流的编码
        request.setCharacterEncoding("utf-8");

        //post 获取请求参数username
        String username = request.getParameter("username");
        System.out.println(username);

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get获取请求参数

        //根据参数名称获取参数值
//        String username = request.getParameter("username");
//        System.out.println("get");
//        System.out.println(username);

        this.doPost(request,response);
    }
}