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Updated SeaweedFS Java Client (markdown)

Chris Lu 2021-02-05 00:30:30 -08:00
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SeaweedFS-Java-Client.md

@ -5,3 +5,59 @@ Here is an SeaweedFS Java API implementation refactored out of the existing code
https://github.com/chrislusf/seaweedfs/tree/master/other/java/examples/src/main/java/com/seaweedfs/examples https://github.com/chrislusf/seaweedfs/tree/master/other/java/examples/src/main/java/com/seaweedfs/examples
Basically this library will be able to read and write directly to the volume servers, and only use filer servers for meta data. Basically this library will be able to read and write directly to the volume servers, and only use filer servers for meta data.
If you use http to read or write directly via filer, the data still needs to go through filer, which is less efficient.
## Read File
```
FilerGrpcClient filerGrpcClient = new FilerGrpcClient("localhost", 18888);
SeaweedInputStream seaweedInputStream = new SeaweedInputStream(filerGrpcClient, "/test.zip");
// next, you can use seaweedInputStream as a normal InputStream
```
## Write File
```
FilerGrpcClient filerGrpcClient = new FilerGrpcClient("localhost", 18888);
SeaweedOutputStream seaweedOutputStream = new SeaweedOutputStream(filerGrpcClient, "/test/"+filename);
// next, you can use seaweedOutputStream as a normal OutputStream
```
## Watch file changes
This API streams meta data changes.
The following is one implementation. It just watch the folder "/buckets" and all the meta data changes under the folder and all sub folders recursively. A bit more code, but should be powerful and simple to use.
```
FilerClient filerClient = new FilerClient("localhost", 18888);
long sinceNs = (System.currentTimeMillis() - 3600 * 1000) * 1000000L;
Iterator<FilerProto.SubscribeMetadataResponse> watch = filerClient.watch(
"/buckets",
"exampleClientName",
sinceNs
);
System.out.println("Connected to filer, subscribing from " + new Date());
while (watch.hasNext()) {
FilerProto.SubscribeMetadataResponse event = watch.next();
FilerProto.EventNotification notification = event.getEventNotification();
if (!event.getDirectory().equals(notification.getNewParentPath())) {
// move an entry to a new directory, possibly with a new name
if (notification.hasOldEntry() && notification.hasNewEntry()) {
System.out.println("moved " + event.getDirectory() + "/" + notification.getOldEntry().getName() + " to " + notification.getNewParentPath() + "/" + notification.getNewEntry().getName());
} else {
System.out.println("this should not happen.");
}
} else if (notification.hasNewEntry() && !notification.hasOldEntry()) {
System.out.println("created entry " + event.getDirectory() + "/" + notification.getNewEntry().getName());
} else if (!notification.hasNewEntry() && notification.hasOldEntry()) {
System.out.println("deleted entry " + event.getDirectory() + "/" + notification.getOldEntry().getName());
} else if (notification.hasNewEntry() && notification.hasOldEntry()) {
System.out.println("updated entry " + event.getDirectory() + "/" + notification.getNewEntry().getName());
}
}
```