对tomcat的源码做一些分析，今天我们就开始servlet中的请求分析。
form表单中的默认类型
一、在index.jsp中get请求：
<form action="ParameterServlet" method="get">
username: <input type="text" name="username"/><br>
password: <input type="password" name="password"/><br>
file:<input type="file" name="file"><br>
<input type="submit" value="submit">
</form>
二、在ParameterServlet中的doGet方法中：
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
ServletInputStream inputStream = request.getInputStream();
System.out.println("queryUrl: " + request.getMethod() + ", data: " + request.getQueryString());
System.out.println("--------------------------------------------------------------------------");
int len;
while((len = inputStream.read()) != -1) {
System.out.print((char)len);
}
inputStream.close();
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
get请求的结果：
queryUrl: GET, data: username=huhx&password=&file=efdjoue.png
--------------------------------------------------------------------------
post请求结果：
queryUrl: POST, data: null
--------------------------------------------------------------------------
username=huhx&password=&file=test.png
三、get和post请求的一些总结
getQueryString方法得到的url中的请求参数部分，而request.getInputStream读取的是请求体的内容。对于get请求来说，从请求流中读取的数据是为空的。
form表单中的multipart类型
修改form表单的enctype为：multipart/form-data
一、index.jsp如下：
<form action="ParameterServlet" method="get" enctype="multipart/form-data">
username: <input type="text" name="username"/><br>
password: <input type="password" name="password"/><br>
file:<input type="file" name="file"><br>
<input type="submit" value="submit">
</form>
get请求的结果和浏览器的地址url：
aaarticlea/png;base64,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" alt="" />
queryUrl: GET, data: username=Linux&password=password&file=efdjoue.png
--------------------------------------------------------------------------
post请求的结果：
queryUrl: POST, data: null
--------------------------------------------------------------------------
-----------------------------
Content-Disposition: form-data; name="username" huhx
-----------------------------
Content-Disposition: form-data; name="password" -----------------------------
Content-Disposition: form-data; name="file"; filename="efdjoue.png"
Content-Type: image/png PNG
....后面是图片的乱码信息，这里省略....
二、在设置了multipart/form-data之后的请求中
- get请求可以使用request.getParameter("username")得到对应的值
- post请求使用request.getParameter("username")得到的是null，getParameter("file")也是null。