Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.beam.sdk.extensions.sql.impl; import static org.apache.calcite.util.Static.RESOURCE; import com.google.common.collect.ImmutableMultimap; import java.lang.reflect.Constructor; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import org.apache.beam.sdk.extensions.sql.impl.utils.CalciteUtils; import org.apache.calcite.adapter.enumerable.CallImplementor; import org.apache.calcite.adapter.enumerable.NullPolicy; import org.apache.calcite.adapter.enumerable.ReflectiveCallNotNullImplementor; import org.apache.calcite.adapter.enumerable.RexImpTable; import org.apache.calcite.linq4j.function.SemiStrict; import org.apache.calcite.linq4j.function.Strict; import org.apache.calcite.rel.type.RelDataType; import org.apache.calcite.rel.type.RelDataTypeFactory; import org.apache.calcite.schema.Function; import org.apache.calcite.schema.ImplementableFunction; import org.apache.calcite.schema.ScalarFunction; import org.apache.calcite.sql.SqlOperatorBinding; /** * Beam-customized version from {@link org.apache.calcite.schema.impl.ScalarFunctionImpl}, to * address BEAM-5921. */ public class ScalarFunctionImpl extends UdfImplReflectiveFunctionBase implements ScalarFunction, ImplementableFunction { private final CallImplementor implementor; /** Private constructor. */ private ScalarFunctionImpl(Method method, CallImplementor implementor) { super(method); this.implementor = implementor; } /** Creates {@link org.apache.calcite.schema.Function} for each method in a given class. */ public static ImmutableMultimap<String, Function> createAll(Class<?> clazz) { final ImmutableMultimap.Builder<String, Function> builder = ImmutableMultimap.builder(); for (Method method : clazz.getMethods()) { if (method.getDeclaringClass() == Object.class) { continue; } if (!Modifier.isStatic(method.getModifiers()) && !classHasPublicZeroArgsConstructor(clazz)) { continue; } final Function function = create(method); builder.put(method.getName(), function); } return builder.build(); } /** * Creates {@link org.apache.calcite.schema.Function} from given class. * * <p>If a method of the given name is not found or it does not suit, returns {@code null}. * * @param clazz class that is used to implement the function * @param methodName Method name (typically "eval") * @return created {@link ScalarFunction} or null */ public static Function create(Class<?> clazz, String methodName) { final Method method = findMethod(clazz, methodName); if (method == null) { return null; } return create(method); } /** * Creates {@link org.apache.calcite.schema.Function} from given method. When {@code eval} method * does not suit, {@code null} is returned. * * @param method method that is used to implement the function * @return created {@link Function} or null */ public static Function create(Method method) { if (!Modifier.isStatic(method.getModifiers())) { Class clazz = method.getDeclaringClass(); if (!classHasPublicZeroArgsConstructor(clazz)) { throw RESOURCE.requireDefaultConstructor(clazz.getName()).ex(); } } if (method.getExceptionTypes().length != 0) { throw new RuntimeException(method.getName() + " must not throw checked exception"); } CallImplementor implementor = createImplementor(method); return new ScalarFunctionImpl(method, implementor); } @Override public RelDataType getReturnType(RelDataTypeFactory typeFactory) { return CalciteUtils.sqlTypeWithAutoCast(typeFactory, method.getReturnType()); } @Override public CallImplementor getImplementor() { return implementor; } private static CallImplementor createImplementor(final Method method) { final NullPolicy nullPolicy = getNullPolicy(method); return RexImpTable.createImplementor(new ReflectiveCallNotNullImplementor(method), nullPolicy, false); } private static NullPolicy getNullPolicy(Method m) { if (m.getAnnotation(Strict.class) != null) { return NullPolicy.STRICT; } else if (m.getAnnotation(SemiStrict.class) != null) { return NullPolicy.SEMI_STRICT; } else if (m.getDeclaringClass().getAnnotation(Strict.class) != null) { return NullPolicy.STRICT; } else if (m.getDeclaringClass().getAnnotation(SemiStrict.class) != null) { return NullPolicy.SEMI_STRICT; } else { return NullPolicy.NONE; } } public RelDataType getReturnType(RelDataTypeFactory typeFactory, SqlOperatorBinding opBinding) { // Strict and semi-strict functions can return null even if their Java // functions return a primitive type. Because when one of their arguments // is null, they won't even be called. final RelDataType returnType = getReturnType(typeFactory); switch (getNullPolicy(method)) { case STRICT: for (RelDataType type : opBinding.collectOperandTypes()) { if (type.isNullable()) { return typeFactory.createTypeWithNullability(returnType, true); } } break; case SEMI_STRICT: return typeFactory.createTypeWithNullability(returnType, true); default: break; } return returnType; } /** * Verifies if given class has public constructor with zero arguments. * * @param clazz class to verify * @return true if given class has public constructor with zero arguments */ static boolean classHasPublicZeroArgsConstructor(Class<?> clazz) { for (Constructor<?> constructor : clazz.getConstructors()) { if (constructor.getParameterTypes().length == 0 && Modifier.isPublic(constructor.getModifiers())) { return true; } } return false; } /* * Finds a method in a given class by name. * @param clazz class to search method in * @param name name of the method to find * @return the first method with matching name or null when no method found */ static Method findMethod(Class<?> clazz, String name) { for (Method method : clazz.getMethods()) { if (method.getName().equals(name) && !method.isBridge()) { return method; } } return null; } } // End ScalarFunctionImpl.java