Java请求参数检查 Java如何检查servlet请求中是否存在参数？

ServletRequest或HttpServletRequest对象具有用于映射参数名称及其值的映射对象。通过访问此映射，我们可以检查servlet请求中是否传递了参数。让我们看下面的例子。packageorg.nhooo.example.servlet;

importjavax.servlet.ServletException;

importjavax.servlet.http.HttpServlet;

importjavax.servlet.http.HttpServletRequest;

importjavax.servlet.http.HttpServletResponse;

importjava.io.IOException;

publicclassParameterCheckextendsHttpServlet{

protectedvoiddoGet(HttpServletRequestreq,HttpServletResponseres)

throwsServletException,IOException{

// 检查用户名参数是否存在

if(req.getParameterMap().containsKey("username")){

Stringusername=req.getParameter("username");

}

// 检查密码参数是否存在

if(req.getParameterMap().containsKey("password")){

Stringpassword=req.getParameter("password");

}

}

}