Servlet：处理许多可选参数 [英] Servlet: Handling many optional parameters

问题描述

只是想知道是否有更优雅或标准的方法来处理可选参数，或者是否必须检查每个参数是否为空。我有10多个可选参数，所以它有点难看。

Just wondering if there is a more elegant or standard way to handle the optional parameters or if you have to check if every one is null. I have 10+ optional parameters so it is getting somewhat ugly.

理想情况下，我想要像bash命令一样： getopts 。

Ideally I would like something like the bash command: getopts.

public class MapImageServlet extends HttpServlet {
    ... constructor and other methods ...
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // OPTIONAL PARAMETERS
        if(request.getParameter("boarderSize") != null){
            double boarderSize = Double.valueOf(request.getParameter("boarderSize");
        }

        if(request.getParameter("boarderThickness") != null){
            double boarderThickness = Double.valueOf(request.getParameter("boarderThickness");
        }

        if(request.getParameter("boarderColor") != null){
            double boarderColor = Double.valueOf(request.getParameter("boarderColor");
        }
        ... do stuff with the parameters ...
    }
    ... other methods ...
}

推荐答案

写一个像这样的实用程序

Write a utility like this

public class MapImageServlet extends HttpServlet {
//... constructor and other methods ...
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    // OPTIONAL PARAMETERS
     boarderSize = ParamUtil.getDoubleValue(request,"boarderSize", defaultValue);

     boarderThickness = ParamUtil.getDoubleValue(request, "boarderThickness", defaultValue);

     boarderColor = ParamUtil.getDoubleValue(request,"boarderColor" , defaultValue);
     //... do stuff with the parameters ...
}

}
public class ParamUtil
{
public static double getDoubleValue(ServletRequest request, String paramName, double defaultValue)
{
     if(request.getParameter(paramName) != null){
        return Double.valueOf(request.getParameter(paramName));
    } else{
        return defaultValue;
    }
}
}

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