How to Trigger File Downloads with Ajax and a Struts2 Action?

Asynchronous File Download Using Ajax

In the provided scenario, you encounter an issue where a Struts2 action is used for file downloading, but jQuery post() call retrieves the file as a binary stream instead of opening a file download window. This article aims to address the problem and provide a solution to prompt the file download window.

The key to enabling file downloads using Ajax lies in utilizing the Content-Disposition response header. This header should be set to attachment; filename={fileName}, where {fileName} represents the desired filename. By setting this header, you instruct the browser to prompt the user with a file download window.

To modify the Content-Disposition header dynamically in your Struts2 action, you can use an interceptor. Here's an example of how you can do this:

public class DownloadInterceptor implements Interceptor {

    @Override
    public String intercept(ActionInvocation invocation) throws Exception {
        HttpServletResponse response = ServletActionContext.getResponse();
        response.setHeader("Content-Disposition", "attachment; filename=" + actionInvocation.getArgs()[0]); // Replace with your code
        return invocation.invoke();
    }

    @Override
    public void destroy() {}

    @Override
    public void init() {}
}

Once you have implemented the interceptor, you can apply it to the download action to dynamically set the Content-Disposition header.

By combining these steps, you can configure your Struts2 application to download files asynchronously using Ajax and allow users to save the files locally.

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