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FieldInjections.java
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FieldInjections.java
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/*
* Copyright (c) 2002-2016 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.kernel.impl.proc;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.LinkedList;
import java.util.List;
import java.util.function.Function;
import org.neo4j.kernel.api.exceptions.ProcedureException;
import org.neo4j.kernel.api.exceptions.Status;
import org.neo4j.kernel.api.proc.CallableProcedure;
import org.neo4j.messages.Messages;
import org.neo4j.procedure.Context;
import static org.neo4j.messages.Messages.proc_static_field_annotated_as_context;
/**
* Injects annotated fields with appropriate values.
*/
public class FieldInjections
{
private final ComponentRegistry components;
public FieldInjections( ComponentRegistry components )
{
this.components = components;
}
/**
* On calling apply, injects the `value` for the field `field` on the provided `object`.
*/
public static class FieldSetter
{
private final Field field;
private final MethodHandle setter;
private final Function<CallableProcedure.Context,?> supplier;
public FieldSetter( Field field, MethodHandle setter, Function<CallableProcedure.Context,?> supplier )
{
this.field = field;
this.setter = setter;
this.supplier = supplier;
}
void apply( CallableProcedure.Context ctx, Object object ) throws ProcedureException
{
try
{
setter.invoke( object, supplier.apply( ctx ) );
}
catch ( Throwable e )
{
throw new ProcedureException( Status.Procedure.CallFailed, e,
"Unable to inject component to field `%s`, please ensure it is public and non-final: %s",
field.getName(), e.getMessage() );
}
}
}
/**
* For each annotated field in the provided class, creates a `FieldSetter`.
* @param cls The class where injection should happen.
* @return A list of `FieldSetters`
* @throws ProcedureException if the type of the injected field does not match what has been registered.
*/
public List<FieldSetter> setters( Class<?> cls ) throws ProcedureException
{
List<FieldSetter> setters = new LinkedList<>();
Class<?> currentClass = cls;
do
{
for ( Field field : currentClass.getDeclaredFields() )
{
if ( Modifier.isStatic( field.getModifiers() ) )
{
if( field.isAnnotationPresent( Context.class ))
{
throw new ProcedureException( Status.Procedure.FailedRegistration,
Messages.get( proc_static_field_annotated_as_context,
field.getName(), cls.getSimpleName() ) );
}
continue;
}
assertValidForInjection( cls, field );
setters.add( createInjector( cls, field ) );
}
} while( (currentClass = currentClass.getSuperclass()) != null );
return setters;
}
private FieldSetter createInjector( Class<?> cls, Field field ) throws ProcedureException
{
try
{
Function<CallableProcedure.Context,?> supplier = components.supplierFor( field.getType() );
if( supplier == null )
{
throw new ProcedureException( Status.Procedure.FailedRegistration,
"Unable to set up injection for procedure `%s`, the field `%s` " +
"has type `%s` which is not a known injectable component.",
cls.getSimpleName(), field.getName(), field.getType());
}
MethodHandle setter = MethodHandles.lookup().unreflectSetter( field );
return new FieldSetter( field, setter, supplier );
}
catch ( IllegalAccessException e )
{
throw new ProcedureException( Status.Procedure.FailedRegistration,
"Unable to set up injection for `%s`, failed to access field `%s`: %s",
e, cls.getSimpleName(), field.getName(), e.getMessage() );
}
}
private void assertValidForInjection( Class<?> cls, Field field ) throws ProcedureException
{
if( !field.isAnnotationPresent( Context.class ) )
{
throw new ProcedureException( Status.Procedure.FailedRegistration,
"Field `%s` on `%s` is not annotated as a @Resource and is not static. " +
"If you want to store state along with your procedure, please use a static field.",
field.getName(), cls.getSimpleName() );
}
if( !Modifier.isPublic( field.getModifiers() ) || Modifier.isFinal( field.getModifiers() ) )
{
throw new ProcedureException( Status.Procedure.FailedRegistration,
"Field `%s` on `%s` must be non-final and public.",
field.getName(), cls.getSimpleName() );
}
}
}