ServletAdaptor.java

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package com.sun.jersey.server.impl.container.servlet;

import com.sun.jersey.server.impl.ThreadLocalNamedInvoker;
import com.sun.jersey.api.container.ContainerException;
import com.sun.jersey.api.core.ResourceConfig;
import com.sun.jersey.spi.container.WebApplication;
import com.sun.jersey.spi.container.servlet.ServletContainer;
import com.sun.jersey.spi.inject.Injectable;
import com.sun.jersey.spi.inject.InjectableProvider;
import com.sun.jersey.core.spi.component.ComponentContext;
import com.sun.jersey.core.spi.component.ComponentScope;
import java.lang.reflect.Proxy;
import java.lang.reflect.Type;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import javax.persistence.EntityManagerFactory;
import javax.persistence.PersistenceUnit;
import javax.servlet.ServletConfig;

/**
 * A servlet container for deploying root resource classes with support
 * for injecting persistence units.
 * <p>
 * Persistence units that may be injected must be configured in web.xml
 * in the normal way plus an additional servlet parameter to enable the
 * Jersey servlet to locate them in JNDI. E.g. with the following
 * persistence unit configuration:
 *
 * <persistence-unit-ref>
 *     <persistence-unit-ref-name>persistence/widget</persistence-unit-ref-name>
 *     <persistence-unit-name>WidgetPU</persistence-unit-name>
 * </persistence-unit-ref>
 *
 * the Jersey servlet requires an additional servlet parameter as
 * follows:
 *
 * <init-param>
 *     <param-name>unit:WidgetPU</param-name>
 *     <param-value>persistence/widget</param-value>
 * </init-param>
 *
 * Given the above, Jersey will inject the EntityManagerFactory found
 * at java:comp/env/persistence/widget in JNDI when encountering a
 * field or parameter annotated with @PersistenceUnit(unitName="WidgetPU").
 */
public class ServletAdaptor extends ServletContainer {
    private Map<String, String> persistenceUnits =
            new HashMap<String, String>();
        
    @Override
    protected void configure(ServletConfig servletConfig, ResourceConfig rc, WebApplication wa) {
        super.configure(servletConfig, rc, wa);

        /**
         * Look for persistent units.
         */
        for (Enumeration e = servletConfig.getInitParameterNames() ; e.hasMoreElements() ;) {
            String key = (String)e.nextElement();
            String value = servletConfig.getInitParameter(key);
            if (key.startsWith("unit:")) {
                persistenceUnits.put(key.substring(5),"java:comp/env/"+value);
            }
        }
        
        rc.getSingletons().add(new InjectableProvider<PersistenceUnit, Type>() {
            @Override
            public ComponentScope getScope() {
                return ComponentScope.Singleton;
            }
            
            @Override
            public Injectable<EntityManagerFactory> getInjectable(ComponentContext ic, PersistenceUnit pu, Type c) {
                if (!c.equals(EntityManagerFactory.class))
                    return null;
                
                // TODO localize error message
                if (!persistenceUnits.containsKey(pu.unitName()))
                    throw new ContainerException("Persistence unit '"+
                            pu.unitName()+
                            "' is not configured as a servlet parameter in web.xml");
                String jndiName = persistenceUnits.get(pu.unitName());
                ThreadLocalNamedInvoker<EntityManagerFactory> emfHandler =
                        new ThreadLocalNamedInvoker<EntityManagerFactory>(jndiName);
                final EntityManagerFactory emf = (EntityManagerFactory) Proxy.newProxyInstance(
                        this.getClass().getClassLoader(),
                        new Class[] { EntityManagerFactory.class },
                        emfHandler);
                
                return new Injectable<EntityManagerFactory>() {
                    @Override
                    public EntityManagerFactory getValue() {
                        return emf;
                    }                    
                };
            }
        });        
    }    
}