Http之请求对象_网络请求任务对象是-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_42974177/article/details/123544117

本文详细介绍了如何使用Servlet处理HTTP请求，包括获取请求行、请求头和请求参数的方法，以及如何解决请求参数中文乱码的问题。通过示例代码展示了HttpServletRequest对象的常用方法，如获取请求方式、请求头、请求参数等，并提供了两种解决POST请求中文乱码的解决方案：先编码再解码或设置字符编码。同时，提到了在Tomcat7.0中处理GET和POST请求中文乱码的注意事项。

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ServletRequest对象包含了请求信息(请求行、请求头、请求体)，通过Servlet的services方法传递的；
HttpServletRequest提供了额外的针对HTTP协议相关的功能。

请求对象获取请求行

@WebServlet("/demo13")
public class Demo13Servlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //getMethod : 获取请求方式
        System.out.println("请求方式 = " + request.getMethod());
        //getContextPath : 获取项目访问路径
        System.out.println("项目访问路径 = " + request.getContextPath());
        //getServletPath : 获取Servlet访问路径
        System.out.println("Servlet访问路径 = " + request.getServletPath());
        //getRemoteAddr : 获取客户端地址
        System.out.println("客户端地址 : " + request.getRemoteAddr());
        //getLocalAddr : 获取服务器地址
        System.out.println("服务器地址 : " + request.getLocalAddr());
        //getRequestURL : 找设备 -> 找tomcat -> 找项目 -> 找资源
        System.out.println("统一资源定位符 : " + request.getRequestURL());
        //getRequestURI : 找项目 -> 找资源
        System.out.println("统一资源标识符 : " + request.getRequestURI());
        //getQueryString(了解) : 获取URL后的参数
        System.out.println("QueryString : " + request.getQueryString());


    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

请求对象获取请求头

@WebServlet("/demo14")
public class Demo14Servlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //getHeader : 根据指定请求头名称获取值
        String userAgent = request.getHeader("User-Agent");
        System.out.println("userAgent = " + userAgent);
        //getHeaders : 根据指定请求头名称获取一组值
        Enumeration<String> headerValues = request.getHeaders("User-Agent");
        while (headerValues.hasMoreElements()) {
            String headerValue = headerValues.nextElement();
            System.out.println("userAgent = " + headerValue);
        }
        //getHeaderNames: 获取所有请求头名称
        Enumeration<String> headerNames = request.getHeaderNames();
        while (headerNames.hasMoreElements()) {
            String headerName = headerNames.nextElement();
            String headerValue = request.getHeader(headerName);
            System.out.println("headerName = " + headerName + " , headerValue = " + headerValue);
        }


    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

请求对象获取请求参数

@WebServlet("/demo15")
public class Demo15Servlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //getParameter : 根据指定请求参数名称获取值
        String username = request.getParameter("username");
        System.out.println("username = " + username);
        String password = request.getParameter("password");
        System.out.println("password = " + password);

        //getParameterValues : 根据指定请求参数名称获取一组值(多选)
        String username2 = request.getParameterValues("username")[0];
        System.out.println("username2 = " + username2);
        String password2 = request.getParameterValues("password")[0];
        System.out.println("password2 = " + password2);

        //getParameterNames : 获取所有请求参数名称
        Enumeration<String> parameterNames = request.getParameterNames();
        while (parameterNames.hasMoreElements()) {
            String parameterName = parameterNames.nextElement();
            String parameterValue = request.getParameter(parameterName);
            System.out.println("parameterName = " + parameterName + " , parameterValue = " + parameterValue);
        }

        //getParameterMap : 获取请求参数，并将其封装成map(键=参数名,值=一组参数值)
        Map<String, String[]> parameterMap = request.getParameterMap();
        Set<Map.Entry<String, String[]>> entrySet = parameterMap.entrySet();
        for (Map.Entry<String, String[]> entry : entrySet) {
            String parameterName = entry.getKey();
            String[] parameterValues = entry.getValue();
            System.out.println("parameterName = " + parameterName + " , parameterValues = " + Arrays.toString(parameterValues));

        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

请求参数的封装

一般都是使用工具类自动封装即可。

User user = new User();
        try {
            BeanUtils.populate(user, request.getParameterMap());
            System.out.println("user = " + user);
        } catch (Exception e) {
            e.printStackTrace();
        }

注意事项

①ClassNotFoundException: org.apache.commons.beanutils.BeanUtils，一般都是jar包导入有问题；javaweb项目，jar包的lib目录应该在WEB-INF目录中。
②使用BeanUtils工具类时，表单中的name属性值和setXxx方法名一致，和javabean中的属性名无关。

请求参数中文乱码问题重点！

GET请求
- 没有请求参数中文乱码问题
POST请求
- 有请求参数中文乱码问题
解决方案
- ①先编码(iso8859-1)，再解码(utf-8)
- ②告诉服务器，以utf-8解码请求正文

方案1：

@WebServlet("/demo18")
public class Demo18Servlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        //先编码(iso8859-1)
        byte[] bys = username.getBytes("iso8859-1");
        //再解码(utf-8)
        username = new String(bys,"utf-8");

        System.out.println("username = " + username);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

解决方案2：

@WebServlet("/demo19")
public class Demo19Servlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //告诉服务器，以utf-8解码请求正文
        request.setCharacterEncoding("utf-8");

        String username = request.getParameter("username");
        System.out.println("username = " + username);

        String password = request.getParameter("password");
        System.out.println("password = " + password);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

tomcat7.0(了解)
- GET请求
  - 有请求参数中文乱码问题
  - ①先编码(iso8859-1)，再解码(utf-8)
  - ②告诉服务器，以utf-8解码路径后参数 ( URIEncoding="UTF-8")
- POST请求
  - 有请求参数中文乱码问题
  - ①先编码(iso8859-1)，再解码(utf-8)
  - ②告诉服务器，以utf-8解码请求正文
注意事项
- request.setCharacterEncoding("utf-8");必须放在所有获取请求参数之前，否则无效!