请求
请求对象介绍
请求：获取资源。在BS架构中，就是客户端浏览器向服务器发出询问
请求对象：就是在项目当中用于发送请求的对象
ServletRequest 和 HttpServletRequest
请求对象的常用方法-获取各种路径
返回值 方法名 说明
String getContextPath() 获取虚拟目录名称
String getServletPath() 获取Servlet映射路径
String getRemoteAddr() 获取访问者ip地址
String getQueryString() 获取请求的消息数据
String getRequestURI() 获取统一资源标识符
StringBuffer getRequestURL() 获取统一资源定位符
package com.itheima.servlet;
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;
@WebServlet("/ServletDemo01")
public class ServletDemo01 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//getContextPath() 获取虚拟目录名称
String contextPath = request.getContextPath();
System.out.println(contextPath);
//getServletPath() 获取Servlet映射路径
String servletPath = request.getServletPath();
System.out.println(servletPath);
//getRemoteAddr() 获取访问者ip地址
String remoteAddr = request.getRemoteAddr();
System.out.println(remoteAddr);
//getQueryString() 获取请求的消息数据 (了解)
String queryString = request.getQueryString();
System.out.println(queryString);
//getRequestURI() 获取统一资源标识符 /request/ServletDemo01 共和国
String requestURI = request.getRequestURI();
System.out.println(requestURI);
//getRequestURL() 获取统一资源定位符 http://localhost:8080/request/ServletDemo01 中华人民共和国
StringBuffer requestURL = request.getRequestURL();
System.out.println(requestURL);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
请求对象常用方法-获取请求头信息
返回值 方法名 说明
String getHeader(String name) 根据请求头名称获取一个值
Enumeration<String> getHeaders(String name) 根据请求头名称获取多个值
Enumeration<String> getHeaderNames() 根据所有请求头名称
package com.itheima.servlet;
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.util.Enumeration;
/*
* 获取请求头信息的相关方法
* */
@WebServlet("/ServletDemo02")
public class ServletDemo02 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//getHeader(String name) 根据请求头名称获取一个值
String connection = request.getHeader("connection");
System.out.println(connection);
System.out.println("----------");
//getHeaders(String name) 根据请求头名称获取多个值
Enumeration<String> values = request.getHeaders("Accept-Encoding");
while(values.hasMoreElements()){
String value = values.nextElement();
System.out.println(value);
}
System.out.println("----------");
//getHeaderNames() 根据所有请求头名称
Enumeration<String> names = request.getHeaderNames();
while(names.hasMoreElements()){
String name = names.nextElement();
String value = request.getHeader(name);
System.out.println(name+","+value);
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
2.3.3 请求对象常用方法3-获取请求参数（非常重要）
返回值 方法名 说明
String getParameter(String name) 根据名称获取数据
String[] getParameterValues(String name) 根据名称获取所有数据
Enumeration<String> getParameterNames() 获取所有名称
Map<String,String[]> getParameterMap() 获取所有参数键值对
package com.itheima.servlet;
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.util.Enumeration;
import java.util.Map;
/*
* 获取请求信息的相关方法
* */
@WebServlet("/ServletDemo03")
public class ServletDemo03 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.根据名称获取数据 getParameter()
String username = request.getParameter("username");
System.out.println(username);
String password = request.getParameter("password");
System.out.println(password);
System.out.println("----------------------");
//2.根据名称获取所有数据 getParameterValues()
String[] hobbies = request.getParameterValues("hobby");
for (String hobby : hobbies) {
System.out.println(hobby);
}
System.out.println("----------------------");
//3.获取所有名称 getParameterNames()
Enumeration<String> names = request.getParameterNames();
while(names.hasMoreElements()){
String name = names.nextElement();
System.out.println(name);
}
System.out.println("----------------------");
//4.获取所有参数的键值对 getParameterMap()
Map<String, String[]> map = request.getParameterMap();
for (String key : map.keySet()) {
String[] values = map.get(key);
System.out.print(key+":");
for (String value : values) {
System.out.print(value+" ");
}
System.out.println();
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
第一种：最简单直接的封装方式
bean/Student
package com.itheima.bean;
import java.util.Arrays;
public class Student {
private String username;
private String password;
private String[] hobby;
public Student() {
}
public Student(String username, String password, String[] hobby) {
this.username = username;
this.password = password;
this.hobby = hobby;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String[] getHobby() {
return hobby;
}
public void setHobby(String[] hobby) {
this.hobby = hobby;
}
@Override
public String toString() {
return "Student{" +
"username='" + username + '\'' +
", password='" + password + '\'' +
", hobby=" + Arrays.toString(hobby) +
'}';
}
}
ServletDemo04:
package com.itheima.servlet;
import com.itheima.bean.Student;
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.util.Enumeration;
import java.util.Map;
/*
* 封装对象-手动封装
* */
@WebServlet("/ServletDemo04")
public class ServletDemo04 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.获取所有的数据
String username = request.getParameter("username");
String password = request.getParameter("password");
String[] hobbies = request.getParameterValues("hobby");
//2.封装学生对象
Student stu=new Student(username,password,hobbies);
//输出对象
System.out.println(stu);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
第二种：使用反射方式封装
package com.itheima.servlet;
import com.itheima.bean.Student;
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.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.io.IOException;
import java.lang.reflect.Method;
import java.util.Map;
/*
* 封装对象-反射方式
* */
@WebServlet("/ServletDemo05")
public class ServletDemo05 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.获取所有的数据
Map<String, String[]> map = request.getParameterMap();
//2.封装学生对象
Student stu=new Student();
//2.1.遍历集合
for (String name : map.keySet()) {
String[] value = map.get(name);
//2.2获取Student对象的属性描述器,根据名称拿到 stu里面的get/set方法
try {
PropertyDescriptor pd=new PropertyDescriptor(name,stu.getClass());
//2.3获取对应的setXXX方法
Method writeMethod = pd.getWriteMethod();
//2.4执行方法
if (value.length >1) {
writeMethod.invoke(stu,(Object) value);
}else{
writeMethod.invoke(stu,value);
}
} catch (Exception e) {
e.printStackTrace();
}
}
//输出对象
System.out.println(stu);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
当我们写完此种封装方式之后，同学们可以发现，我们绝大多数封装都可以使用这段代码来实现。并且，无论是谁来写这段通用的封装代码，其代码内容都是大同小异的。那么，我们就可以得出一个很有趣的结论：一般遇到这种情况时，肯定有人帮我们写好了，我们只需要用就行了。我们后面还会遇到类似这样的情况。
此时，帮我们写好这段封装代码的是apache软件基金会，我们前面学习的tomcat也是它提供的。它里面有一个开源工具包集合commons，里面有很多开源工具类，今天我们就来讲解第一个：commons-beanutils。
第三种：使用工具类封装方式
导入这两个包
package com.itheima.servlet;
import com.itheima.bean.Student;
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.beans.PropertyDescriptor;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Map;
/*
* 封装对象-工具类方式
* */
@WebServlet("/ServletDemo06")
public class ServletDemo06 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.获取所有的数据
Map<String, String[]> map = request.getParameterMap();
//2.封装学生对象
Student stu=new Student();
try {
BeanUtils.populate(stu,map);
} catch (Exception e) {
e.printStackTrace();
}
//输出对象
System.out.println(stu);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
通过流对象获取请求信息
返回值 方法名 说明
BufferReader getReader() 获取字符输入流
ServletInputStream getInputStream() 获取字节输入流
package com.itheima.servlet;
import com.itheima.bean.Student;
import org.apache.commons.beanutils.BeanUtils;
import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedReader;
import java.io.IOException;
import java.util.Map;
/*
* 流对象获取数据
* */
@WebServlet("/ServletDemo07")
public class ServletDemo07 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//字符流(必须是post方式)
/* BufferedReader br = request.getReader();
String line;
while((line=br.readLine())!=null){
System.out.println(line);
}*/
//br.close();
//字节流
ServletInputStream is = request.getInputStream();
byte[] arr=new byte[1024];
int len;
while((len= is.read(arr))!=-1){
System.out.println(new String(arr,0,len));
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
2.3.5请求正文中中文编码问题
关于请求中文乱码问题，我们需要分开讨论，第一是POST请求方式，第二是GET方式。
1）POST方式请求
在POST方式请求中，我们的乱码问题可以用如下代码解决：
request.setCharacterEncoding("UTF-8");
GET方式请求的正文是在地址栏中，在Tomcat8.5版本及以后，Tomcat服务器已经帮我们解决了，所以不会有乱码问题了。
而如果我们使用的不是Tomcat服务器，或者Tomcat的版本是8.5以前，那么GET方式仍然会有乱码问题，解决方式如下：（以下代码了解即可，因为我们现在使用的是Tomcat9.0.27版本）
/**
* 在Servlet的doGet方法中添加如下代码
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
/*
* GET方式：正文在地址栏
* username=%D5%C5%C8%FD
* %D5%C5%C8%FD是已经被编过一次码了
*
* 解决办法：
* 使用正确的码表对已经编过码的数据进行解码。
* 就是把取出的内容转成一个字节数组，但是要使用正确的码表。（ISO-8859-1）
* 再使用正确的码表进行编码
* 把字节数组再转成一个字符串，需要使用正确的码表，是看浏览器当时用的是什么码表
*/
String username = request.getParameter("username");
byte[] by = username.getBytes("ISO-8859-1");
username = new String(by,"GBK");
//输出到浏览器：注意响应的乱码问题已经解决了
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.write(username);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
请求对象
请求域(request域)：可以在一次请求范围内进行共享数据
请求对象操作共享数据方法
返回值 方法名 说明
void setAttribute(String name,Object value) 向请求域对象中存储数据
Object getAttribute(String name) 通过名称获取请求域对象中的数据
void removeAttribute(String name) 通过名称一处请求域对象中的数据
2.3.6 请求转发（与重定向的区别）
在实际开发中，重定向和请求转发都是我们要用到的响应方式，那么他们有什么区别呢？我们通过下面的示例来看一下：
请求转发：客户端的一次请求到达后，发现需要借助其他Servlet来实现功能
特点：
- 浏览器地址栏不变
- 域对象中的数据不丢失
- 负责转发的Servlet转发前后的相应正文会丢失
- 有转发的目的地来响应客户端
返回值 方法名 说明
RequestDispatcher getRequestDispatcher(String name) 获取请求调度对象
返回值 方法名 说明
void forward(ServletRequest req,ServletResponse resp) 实现转发
ServletDemo09
package com.itheima.servlet;
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;
/*
* 请求转发
* */
@WebServlet("/ServletDemo09")
public class ServletDemo09 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
//设置共享数据
request.setAttribute("encoding","gbk");
//获取请求调度对象
request.getRequestDispatcher("/ServletDemo10").forward(request,response);
}
}
ServletDemo10
package com.itheima.servlet;
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;
/*
* 请求转发
* */
@WebServlet("/ServletDemo10")
public class ServletDemo10 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取共享数据
Object encoding = request.getAttribute("encoding");
System.out.println(encoding);
System.out.println("ServletDemo10执行了");
}
}
2.3.7 请求包含
在实际开发中，我们可能需要把两个Servlet的内容合并到一起来响应浏览器，而同学们都知道HTTP协议的特点是一请求，一响应的方式。所以绝对不可能出现有两个Servlet同时响应方式。那么我们就需要用到请求包含，把两个Servlet的响应内容合并输出。我们看具体使用示例：
请求包含：可以合并其他Servlet中的功能一起响应给客户端
返回值 方法名 说明
RequestDispatcher getRequestDispatcher(String name) 获取请求调度对象
返回值 方法名 说明
void include(ServletRequest req,ServletReponse resp) 实现包含
ServletDemo13
package com.itheima.servlet;
import javax.servlet.RequestDispatcher;
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;
/*
请求包含
*/
//@WebServlet(name = "ServletDemo09",urlPatterns = "/ServletDemo09")
@WebServlet("/ServletDemo13")
public class ServletDemo13 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("ServletDemo13执行了");
//获取请求的调度对象
req.getRequestDispatcher("/ServletDemo14").include(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req,resp);
}
}
ServletDemo14
package com.itheima.servlet;
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;
/*
请求包含
*/
//@WebServlet(name = "ServletDemo09",urlPatterns = "/ServletDemo09")
@WebServlet("/ServletDemo14")
public class ServletDemo14 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("ServletDemo14执行了");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req,resp);
}
}
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