Java tutorial
/** * Entity Essentials -- A Component-based Entity System * * Copyright (C) 2015 Elmar Schug <elmar.schug@jayware.org>, * Markus Neubauer <markus.neubauer@jayware.org> * * This file is part of Entity Essentials. * * Entity Essentials is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public License * as published by the Free Software Foundation, either version 3 of * the License, or any later version. * * Entity Essentials 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 * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ package org.jayware.e2.component.impl.generation.writer; import org.jayware.e2.component.api.AbstractComponent; import org.jayware.e2.component.api.ComponentFactoryException; import org.jayware.e2.component.api.ComponentManager; import org.jayware.e2.component.api.ComponentMarshalException; import org.jayware.e2.component.api.ComponentPropertyAdapter; import org.jayware.e2.component.impl.generation.plan.ComponentGenerationPlan; import org.jayware.e2.component.impl.generation.plan.ComponentPropertyGenerationPlan; import org.jayware.e2.context.api.Context; import org.objectweb.asm.ClassWriter; import org.objectweb.asm.Label; import org.objectweb.asm.MethodVisitor; import org.objectweb.asm.Type; import java.util.Arrays; import static org.objectweb.asm.Opcodes.ACC_PUBLIC; import static org.objectweb.asm.Opcodes.ACONST_NULL; import static org.objectweb.asm.Opcodes.ALOAD; import static org.objectweb.asm.Opcodes.ARETURN; import static org.objectweb.asm.Opcodes.ASTORE; import static org.objectweb.asm.Opcodes.ATHROW; import static org.objectweb.asm.Opcodes.DUP; import static org.objectweb.asm.Opcodes.GETFIELD; import static org.objectweb.asm.Opcodes.GOTO; import static org.objectweb.asm.Opcodes.IFEQ; import static org.objectweb.asm.Opcodes.IFNONNULL; import static org.objectweb.asm.Opcodes.INVOKEINTERFACE; import static org.objectweb.asm.Opcodes.INVOKESPECIAL; import static org.objectweb.asm.Opcodes.INVOKESTATIC; import static org.objectweb.asm.Opcodes.INVOKEVIRTUAL; import static org.objectweb.asm.Opcodes.NEW; import static org.objectweb.asm.Type.getDescriptor; import static org.objectweb.asm.Type.getInternalName; import static org.objectweb.asm.Type.getType; public class ComponentGetMethodWriter { public void writeGetMethodFor(ComponentGenerationPlan componentPlan) { final String classInternalName = componentPlan.getGeneratedClassInternalName(); final ClassWriter classWriter = componentPlan.getClassWriter(); final MethodVisitor visitor = classWriter.visitMethod(ACC_PUBLIC, "get", "(Ljava/lang/String;)Ljava/lang/String;", null, null); visitor.visitCode(); for (ComponentPropertyGenerationPlan propertyPlan : componentPlan.getComponentPropertyGenerationPlans()) { final String propertyName = propertyPlan.getPropertyName(); final Class<?> propertyType = propertyPlan.getPropertyType(); final String propertyTypeDescriptor = Type.getDescriptor(propertyPlan.getPropertyType()); final Label endIfPropertyNameEqualsLabel = new Label(); visitor.visitLdcInsn(propertyName); visitor.visitVarInsn(ALOAD, 1); visitor.visitMethodInsn(INVOKEVIRTUAL, getInternalName(String.class), "equals", "(Ljava/lang/Object;)Z", false); visitor.visitJumpInsn(IFEQ, endIfPropertyNameEqualsLabel); if (propertyType.isPrimitive() || propertyType.isArray() && propertyType.getComponentType().isPrimitive()) { if (propertyType.isArray()) { visitor.visitVarInsn(ALOAD, 0); visitor.visitFieldInsn(GETFIELD, classInternalName, propertyName, propertyTypeDescriptor); visitor.visitMethodInsn(INVOKESTATIC, getInternalName(Arrays.class), "toString", "(" + propertyTypeDescriptor + ")" + getDescriptor(String.class), false); } else { visitor.visitVarInsn(ALOAD, 0); visitor.visitFieldInsn(GETFIELD, classInternalName, propertyName, propertyTypeDescriptor); visitor.visitMethodInsn(INVOKESTATIC, "java/lang/String", "valueOf", "(" + propertyTypeDescriptor + ")Ljava/lang/String;", false); } } else if (propertyType.isEnum()) { final Label ifEnumValueNonNull = new Label(); final Label endIf = new Label(); visitor.visitVarInsn(ALOAD, 0); visitor.visitFieldInsn(GETFIELD, classInternalName, propertyName, propertyTypeDescriptor); visitor.visitVarInsn(ASTORE, 2); visitor.visitVarInsn(ALOAD, 2); visitor.visitJumpInsn(IFNONNULL, ifEnumValueNonNull); visitor.visitInsn(ACONST_NULL); visitor.visitJumpInsn(GOTO, endIf); visitor.visitLabel(ifEnumValueNonNull); visitor.visitVarInsn(ALOAD, 2); visitor.visitMethodInsn(INVOKEVIRTUAL, getInternalName(Enum.class), "name", "()Ljava/lang/String;", false); visitor.visitLabel(endIf); } else if (String.class.equals(propertyType)) { visitor.visitVarInsn(ALOAD, 0); visitor.visitFieldInsn(GETFIELD, classInternalName, propertyName, propertyTypeDescriptor); } else if (!propertyType.isPrimitive() || propertyType.isArray() && !propertyType.getComponentType().isPrimitive()) { final Label endIfAdapterNull = new Label(); visitor.visitVarInsn(ALOAD, 0); visitor.visitFieldInsn(GETFIELD, getInternalName(AbstractComponent.class), "myComponentManager", getDescriptor(ComponentManager.class)); visitor.visitVarInsn(ALOAD, 0); visitor.visitFieldInsn(GETFIELD, getInternalName(AbstractComponent.class), "myContext", getDescriptor(Context.class)); visitor.visitLdcInsn(getType(propertyType)); visitor.visitMethodInsn(INVOKEINTERFACE, getInternalName(ComponentManager.class), "getPropertyAdapter", "(" + getDescriptor(Context.class) + getDescriptor(Class.class) + ")" + getDescriptor(ComponentPropertyAdapter.class), true); visitor.visitVarInsn(ASTORE, 2); visitor.visitVarInsn(ALOAD, 2); visitor.visitJumpInsn(IFNONNULL, endIfAdapterNull); visitor.visitTypeInsn(NEW, getInternalName(ComponentMarshalException.class)); visitor.visitInsn(DUP); visitor.visitLdcInsn("No property adapter found for property '" + propertyName + "' of type '" + propertyType.getName() + "'"); visitor.visitMethodInsn(INVOKESPECIAL, getInternalName(ComponentMarshalException.class), "<init>", "(" + getDescriptor(String.class) + ")V", false); visitor.visitInsn(ATHROW); visitor.visitLabel(endIfAdapterNull); visitor.visitVarInsn(ALOAD, 2); visitor.visitVarInsn(ALOAD, 0); visitor.visitFieldInsn(GETFIELD, getInternalName(AbstractComponent.class), "myContext", getDescriptor(Context.class)); visitor.visitVarInsn(ALOAD, 0); visitor.visitFieldInsn(GETFIELD, classInternalName, propertyName, propertyTypeDescriptor); visitor.visitMethodInsn(INVOKEINTERFACE, getInternalName(ComponentPropertyAdapter.class), "marshal", "(" + getDescriptor(Context.class) + getDescriptor(Object.class) + ")" + getDescriptor(String.class), true); } else { throw new ComponentFactoryException(); } visitor.visitInsn(ARETURN); visitor.visitLabel(endIfPropertyNameEqualsLabel); } visitor.visitInsn(ACONST_NULL); visitor.visitInsn(ARETURN); visitor.visitMaxs(0, 0); visitor.visitEnd(); } }