Struts2使用redirect结果类型遇404错误及学习相关疑问求助

Hey there! As someone who’s stumbled through the Struts 2 learning curve before, let’s break down your questions and tackle that frustrating 404 error head-on.

1. Better Ways to Learn the Redirect Result Type #

Skip just copying tutorial code—here’s how to build a solid understanding:

• Master core distinctions first: Don’t mix up redirect and redirectAction. redirect sends a raw HTTP redirect to any URL, while redirectAction is Struts-specific and properly maps to other actions in your app (handling namespaces and action rules automatically).
• Build tiny, focused demos: Start with the simplest case: an action that redirects to another empty action. Then add parameters to the redirect, and tweak namespace settings to see how they affect the target URL. This hands-on testing beats passive reading every time.
• Debug the request flow: Use your browser’s Network tab to watch the HTTP requests when you click the button. You’ll see the initial request, the redirect response, and the final target URL—this makes it easy to spot if the redirect is pointing to a non-existent path.
• Cross-reference official docs: The official Struts 2 docs have detailed, version-specific examples for redirectAction (like cross-namespace redirects or passing parameters). They also call out common pitfalls that tutorials might skip.

2. Can Struts Version Cause the 404 Error? #

Absolutely—version mismatches are one of the top culprits for new learners:

• DTD declaration mismatches: If you’re using a newer Struts 2 version (e.g., 2.5+) but your struts.xml uses an old DTD (like 2.0), the configuration won’t parse correctly. Struts won’t recognize your action mappings, leading straight to a 404. Always match your DTD to your jar version.
• Namespace and action rules: Struts 2.5 tightened up namespace and action name matching. For example, if the tutorial uses an implicit default namespace but your newer version requires explicit namespace attributes, your action won’t be found.
• Security restrictions: Newer Struts versions disable dynamic method calls by default. If the tutorial uses syntax like actionName!methodName in the form action, this will fail unless you explicitly enable it (though this isn’t recommended for production).
• Jar conflicts: Mixing old and new Struts jars can break action mapping entirely. Stick to a consistent set of jars from the same release.

3. Did You Miss Something From the Tutorial? #

Small, easy-to-overlook details are often the cause—here’s what to double-check:

• Struts.xml configuration: Verify your redirectAction result has the correct actionName and namespace attributes. For example:

  <result name="success" type="redirectAction">
      <param name="actionName">hello</param>
      <param name="namespace">/</param>
  </result>
  

  Omitting the namespace might make Struts look in the wrong path.
• JSP form action: Make sure your <s:form> tag’s action attribute exactly matches the name of the action that triggers the redirect. Typos here send requests to non-existent actions.
• Web.xml filter setup: Confirm the Struts 2 filter is mapped to /* so it handles all requests. Mapping it only to .action URLs can break redirects if the target uses a different pattern.
• Deployment path: When running your app, the base URL includes your project name (e.g., http://localhost:8080/MyStrutsApp/). If your form uses a relative path, ensure it’s correct relative to this base.
• Console logs: Check your server’s console for configuration errors (like invalid XML in struts.xml or missing jars). These logs almost always have clues about why the action isn’t being found.

内容的提问来源于stack exchange，提问作者Tel lui