This topic is about Google Guice – Provider Interface.
As @provides method becomes more complex, these methods can be moved to seperate classes using Provider interface.
class SpellCheckerProvider implements Provider<SpellChecker>{
@Override
public SpellChecker get() {
String dbUrl = "jdbc:mysql://localhost:5326/emp";
String user = "user";
int timeout = 100;
SpellChecker SpellChecker = new SpellCheckerImpl(dbUrl, user, timeout);
return SpellChecker;
}
}
Next step is to map the provider to type.
bind(SpellChecker.class).toProvider(SpellCheckerProvider.class);
See the complete example below.
Complete Example
Create a java class named GuiceTester.
GuiceTester.java
import com.google.inject.AbstractModule;
import com.google.inject.Guice;
import com.google.inject.Inject;
import com.google.inject.Injector;
import com.google.inject.Provider;
public class GuiceTester {
public static void main(String[] args) {
Injector injector = Guice.createInjector(new TextEditorModule());
TextEditor editor = injector.getInstance(TextEditor.class);
editor.makeSpellCheck();
}
}
class TextEditor {
private SpellChecker spellChecker;
@Inject
public TextEditor( SpellChecker spellChecker) {
this.spellChecker = spellChecker;
}
public void makeSpellCheck(){
spellChecker.checkSpelling();
}
}
//Binding Module
class TextEditorModule extends AbstractModule {
@Override
protected void configure() {
bind(SpellChecker.class)
.toProvider(SpellCheckerProvider.class);
}
}
//spell checker interface
interface SpellChecker {
public void checkSpelling();
}
//spell checker implementation
class SpellCheckerImpl implements SpellChecker {
private String dbUrl;
private String user;
private Integer timeout;
@Inject
public SpellCheckerImpl(String dbUrl,
String user,
Integer timeout){
this.dbUrl = dbUrl;
this.user = user;
this.timeout = timeout;
}
@Override
public void checkSpelling() {
System.out.println("Inside checkSpelling." );
System.out.println(dbUrl);
System.out.println(user);
System.out.println(timeout);
}
}
class SpellCheckerProvider implements Provider<SpellChecker>{
@Override
public SpellChecker get() {
String dbUrl = "jdbc:mysql://localhost:5326/emp";
String user = "user";
int timeout = 100;
SpellChecker SpellChecker = new SpellCheckerImpl(dbUrl, user, timeout);
return SpellChecker;
}
}
Output
Compile and run the file, you will see the following output.
Inside checkSpelling. jdbc:mysql://localhost:5326/emp user 100
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