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import java.io.File;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.Callable;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlAnyElement;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlID;
import javax.xml.bind.annotation.XmlIDREF;
import javax.xml.bind.annotation.XmlRootElement;
import com.sun.xml.bind.IDResolver;
import com.sun.xml.bind.api.ClassResolver;
/**
* Miniture DI container.
*
* @author Kohsuke Kawaguchi
*/
@XmlRootElement
public class Container {
@XmlElement(name="value")
private List<Value> values = new ArrayList<Value>();
private static class Value {
/**
* ID to identify {@link #value}.
*/
@XmlAttribute(required=true)
@XmlID
private String id;
/**
* This annotation causes JAXB to trigger {@link ClassResolver}
* on this field.
*/
@XmlAnyElement(lax=true)
private Object value;
}
public static Container load(File file) throws JAXBException {
Unmarshaller u = CONTEXT.createUnmarshaller();
// register ClassResolver
u.setProperty(ClassResolver.class.getName(), new ClassResolverImpl());
u.setProperty(IDResolver.class.getName(), new IDResolverImpl());
return (Container)u.unmarshal(file);
}
/**
* Informs JAXB lazily to use such and such class for unmarshalling.
*/
static final class ClassResolverImpl extends ClassResolver {
public Class<?> resolveElementName(String nsUri, String localName) throws Exception {
// assume that element names look like
// <p:ClassName xmlns:p="java:package.name">
// and try to load that class.
if(nsUri.startsWith("java:")) {
String className = nsUri.substring(5)+'.'+localName;
// if an exception is thrown from here, it will be passed to
// ValidationEventHandler
return Class.forName(className);
}
// returning null means 'I have no clue about this element'
return null;
}
}
/**
* Notice that this example places the ID attribute on {@link Value},
* not on the bean object ({@link Value#value}.) So we use
* a custom {@link IDResolver} so that {@link XmlIDREF} resolves
* into the {@link Value#value}.
*/
static final class IDResolverImpl extends IDResolver {
private final Map<String,Object> table = new HashMap<String,Object>();
public void bind(String id, Object obj) {
table.put(id,obj);
}
public Callable<?> resolve(final String id, Class targetType) {
return new Callable<Object>() {
public Object call() throws Exception {
// if IDREF resolves to a Value object,
// use the inner value
Object o = table.get(id);
if(o instanceof Value) {
return ((Value)o).value;
}
return o;
}
};
}
}
/**
* Gets the object for the ID.
*/
public Object get(String id) {
for (Value v : values) {
if(v.id.equals(id))
return v.value;
}
return null;
}
/**
* Note that this {@link JAXBContext} only knows about
* {@link Container}.
*/
private static final JAXBContext CONTEXT;
static {
try {
CONTEXT = JAXBContext.newInstance(Container.class);
} catch (JAXBException e) {
// this is a deployment error
throw new Error(e);
}
}
}