Hello,
i defined the following interface:
@ImplementedBy(FileSystem.class)
public interface IFileSystem {
public String getFileContent(String filepath) throws IOException;
public long getLastModified(String filepath) throws IOException;
}
and implementing class:
@Singleton
public class FileReader implements IFileReader {
@Override
public String getFileContent(String filepath) throws IOException {
return FileUtils.readFileToString(new File(filepath));
}
@Override
public String getLastModified(String filepath) throws IOException {
return (new File(filepath)).lastModified();
}
}
This should encapsulate these file operations on the harddisk. And I'm also
able to mock this interface while testing my classes.
Now i would like to provide a CachedFileReader implementing which should
cache any file *(I keep the example as small as possible without take note
on file changes or anything else)*:
@Singleton
public class CachedFileReader implements IFileReader {
private final HashMap<String, String> cache = new HashMap<String, String>
();
private final IFileReader filereader;
@Override
public String getFileContent(String filepath) throws IOException {
String key = filepath + String.valueOf(getLastModified(filepath)); // I
know this is a crap solution, its just for this example
if (!(cache.containsKey(filepath)) {
cache.put(filepath, filereader.getFileContent(filepath));
}
return cache.get(filepath);
}
@Override
public String getLastModified(String filepath) throws IOException {
return filereader.getLastModified(filepath);
}
@Inject
public CachedFileReader(IFileReader filereader) {
this.filereader = filereader;
}
}
I haven't inherited from FileReader because I want later be able to test
the CachedFileReader itself with a IFileReader mock object passed to the
constructor.
Also I changed the @ImplementedBy Annotation of my IFileReader interface to
CachedFileReader. So every class which needs a IFileReader now gets the
CachedFileReader instance.
But how can I tell Google Juice tell that it should inject the normal
FileReader to the constructor of the CachedFileReader instead of itself? Is
there an annotation for that? I have read about multibindings but it didn't
helped me. Or is there a better solution for my concern?
Thank you in advance,
Dirk
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