JavaEE精选-Request

Enumeration<String> headerNames = request.getHeaderNames();
        while (headerNames.hasMoreElements()){
            String headerName = headerNames.nextElement();
            String headerValue = request.getHeader(headerName);
            System.out.println(headerName + ":" + headerValue);
        }

Enumeration<String> parameterNames = request.getParameterNames();
        while (parameterNames.hasMoreElements()){
            String key = parameterNames.nextElement();
            String[] values = request.getParameterValues(key);
            if(values.length == 1){
                System.out.println(key + ":" + values[0]);
            }else {
                System.out.println(key + ":" + Arrays.toString(values));
            }
        }

req.getServletPath() = requestURI - 应用名 相当于是获取资源的相对路径名

req.getContextPath() //获取应用名

package com.fh.ServletReq;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.lang.reflect.Method;
import java.util.Enumeration;
//通过反射获取请求参数并封装到对象
@WebServlet("/ref")
public class GetParamServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Class<?> user = null;
        User u = null;
        try {
            user = Class.forName("com.fh.ServletReq.User"); //获取字节码文件
            u = (User) user.newInstance(); //实例化
        } catch (Exception e) {
            e.printStackTrace();
        }
        //首先得拿到请求参数的key和value
        Enumeration<String> parameterNames = req.getParameterNames();
        while (parameterNames.hasMoreElements()) {
            String key = parameterNames.nextElement();
            String[] values = req.getParameterValues(key);
            String upKey = key.substring(0, 1).toUpperCase() + key.substring(1); //key就是用来封装的方法的名字，将首字母大写
            try {
                Method set = user.getDeclaredMethod("set" + upKey, String.class);//调用set方法，这里一定要注意参数列表需要匹配
                if (values.length == 1) { //当values长度为1时，直接放入
                    set.invoke(u, values[0]);
                } else { //长度大于1需要使用StringBuilder来拼接
                    StringBuilder sb = new StringBuilder();
                    for (int i = 0; i < values.length; i++) {
                        if (i == values.length - 1) {
                            sb.append(values[i]);
                        } else {
                            sb.append(values[i]).append(",");
                        }
                    }
                    String s = sb.toString();
                    set.invoke(u, s);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        System.out.println(u);
    }
}

package com.fh.ServletReq;
import org.apache.commons.beanutils.BeanUtils;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
@WebServlet("/reg2")
public class RegServlet2 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        User user = new User();
        try {
            BeanUtils.populate(user,req.getParameterMap());
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        System.out.println(user);
    }
}

package com.cskaoyan.request.forward;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
 * @ClassName ${NAME}
 * @Description: TODO
 * @Author 远志 zhangsong@cskaoyan.onaliyun.com
 * @Date 2021/12/9 11:15
 * @Version V1.0
 **/
@WebServlet("/forward1")
public class ForwardServlet1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //访问forward1，需要在代码中去调用forward2，把2里面的数据显示出来
        System.out.println("forward1");
        //需要在forward1中去调用forward2
        //千万不要自己去new一个servlet，然后调用service
        //生命周期应该交由tomcat来统一管理
        //你去给tomcat发送一个指令，让tomcat去调用它
        //这行代码的作用是给tomcat发送一个指令，告诉tomcat去加载当前应用下的/forward2
        //tomcat就去加载forward2，如果它之前没有被访问过，首先实例化；如果访问过，直接调用service方法
        //记住唯一的特殊情况：tomcat的转发中/开头不要加应用名
        //看路径的解析执行主体是谁，如果是浏览器，则/应用名/资源路径，如果是服务器，则/资源路径
        request.getRequestDispatcher("/forward2").forward(request, response);
    }
}

ackage com.cskaoyan.request.forward;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
 * @ClassName ${NAME}
 * @Description: TODO
 * @Author 远志 zhangsong@cskaoyan.onaliyun.com
 * @Date 2021/12/9 11:15
 * @Version V1.0
 **/
@WebServlet("/forward2")
public class ForwardServlet2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("forward2");
    }
}