http之HttpServletRequest和HttpServletResponse

对于客户端的一个请求，服务端建立request和response对象，分别代表请求和返回。

 

一、HttpServletRequest对象

   客户端通过http协议访问时，请求中所有的信息都存放在该对象中，包括parameter name和value，attribute，

input stream，cookie，http协议相关的信息等。

 

1、parameter和attribute的区别

parameter是客户端提交的参数；

attribute是与客户端无关，在不同servlet之间传递参数，当做容器使用

 

设置：

 String white = (String) request.setAttribute(“name”,"china");

 

读取：

 

String white = (String) request.getAttribute(“name”);

2、Cookie

Cookies are passed as HTTP headers, both in the request (client -> server), and in the response (server -> client).

cookie是当做http头部信息存储k-v形式存储，key固定为Cookie，v为name=value形式，多个键值以分号分割。

服务端读取cookie

//简便的获取cookie信息的方式
Cookie[] cookies = request.getCookies();
for(Cookie cookie : cookies){
    log.info("name={},value={}",cookie.getName(),cookie.getValue());
}
//原始的从头部获取cookie的方式
String rawCookie = request.getHeader("Cookie");
String[] rawCookieParams = rawCookie.split(";");
for(String cookie : rawCookieParams){
    log.info("cookie={}",cookie);
}

 

 

参考：

https://*.com/questions/33690741/httpservletrequest-getcookies-or-getheader

 

3、inputStream

ServletInputStream servletInputStream = request.getInputStream();

参考JAVA API解释

可以看出为客户端请求的字节流，一般框架已经封装好，使用较少。 

public abstract class ServletInputStream
extends InputStream

Provides an input stream for reading binary data from a client request, including an efficient readLine method for reading data one line at a time. With some protocols, such as HTTP POST and PUT, a ServletInputStream object can be used to read data sent from the client.

A ServletInputStream object is normally retrieved via the ServletRequest.getInputStream() method.

This is an abstract class that a servlet container implements. Subclasses of this class must implement the java.io.InputStream.read() method.

 

 二、HttpServletReponse对象

 //设置http返回码：404、200等
resp.setStatus(HttpServletResponse.SC_NOT_FOUND);
resp.setContentType("application/json;charset=UTF-8");
String data = "这是字节流输出的内容";
 byte[] dataByteArr = data.getBytes(StandardCharsets.UTF_8);
//获取http输出字节流
 //resp.getOutputStream().write(dataByteArr);
 //resp.flushBuffer();
//获取http输出字符流
resp.getWriter().println("这是字符流输出的内容");

 获取字节流还是字符流只能选择一种。