An Ewon Java application compiles after importing Apache Commons Net 1.4.1, but the JVM stops when it constructs FTPClient. The available runtime inspection found multiple missing classes on the target. This separates the problem from FTP login, directory permissions, and file-listing logic: execution fails before an FTP operation begins.
Observed Failure Boundary
Eclipse accepts the wildcard import and reports no compilation error. On the Ewon target, execution stops at the constructor shown below; commenting out that statement prevents the stop.
import org.apache.commons.net.ftp.*;
FTPClient Myftp = new FTPClient();A successful desktop compilation confirms that the compiler can resolve the library during the build. It does not confirm that every class required by the library exists in the Ewon runtime.
Runtime Compatibility Finding
Inspection of the library source identified multiple classes missing from the Ewon environment. The evidence therefore supports a runtime dependency or API-availability mismatch as the immediate cause. The cited Commons Net 1.4.1 release-note statement about compiler V1.3 compatibility is not enough to establish compatibility with this JVM; the evidence does not define whether that statement covers only compilation, bytecode level, or the complete runtime API.
Do not diagnose FTP credentials, server reachability, or remote-directory permissions until new FTPClient() executes successfully. Those factors cannot explain a stop that occurs during client construction.
Library and Native-Function Decision
| Option | Evidence-supported result | Decision |
|---|---|---|
| Apache Commons Net 1.4.1 | Compiles in Eclipse, but construction of FTPClient stops on the target; source inspection reveals missing target classes. |
Do not deploy unchanged. First resolve every missing runtime class or reject the library as incompatible. |
| ftp4j 1.7.2 | Requires Java Runtime Environment J2SE 1.4 or later. | Use only if the target runtime satisfies that stated requirement and all referenced classes are present. |
| Existing Ewon FTP functions | The existing approach can upload and delete files, but the available proprietary function does not provide remote file listing. | Suitable for known paths; insufficient for discovering files before deleting them. |
Diagnostic and Selection Procedure
- Keep the constructor as the minimum reproduction point and confirm that the JVM stops before any connection or authentication call.
- Inspect the library references and enumerate every class absent from the Ewon runtime. A partial list is not sufficient for declaring compatibility.
- Separate compiler compatibility from runtime compatibility. Treat the V1.3 release-note wording as ambiguous until its scope is established.
- If evaluating ftp4j 1.7.2, verify that the target provides J2SE 1.4 or later and all classes required by the library.
- If neither library matches the target runtime, redesign the workflow around supported Ewon FTP operations or another approach that does not require remote directory enumeration.
Verification is complete only when the client constructor runs on the target without stopping and the selected implementation can return the remote directory listing needed to drive deletion. Successful upload or deletion of a known filename does not verify listing support.
FAQ
Why does Commons Net 1.4.1 compile in Eclipse but stop on Ewon?
The build environment can resolve the imported classes, while the Ewon runtime lacks multiple classes referenced by the library. Compilation success therefore does not prove target-runtime compatibility.
Does Commons Net 1.4.1 compiler V1.3 compatibility guarantee Ewon support?
No. The evidence does not define whether that release-note statement covers compilation, bytecode, or all required runtime classes, so verify the target class set directly.
Can Ewon SendFtp list files on a remote FTP server?
The available evidence says the proprietary FTP function does not integrate remote file listing. It can support operations on known files, but it cannot supply the directory enumeration required to discover each file for deletion.
