| /* |
| * |
| * 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.metron.stellar.common; |
| |
| import com.google.common.collect.ImmutableMap; |
| import org.apache.commons.lang.ClassUtils; |
| import org.apache.metron.stellar.dsl.Context; |
| import org.apache.metron.stellar.dsl.functions.resolver.FunctionResolver; |
| import org.apache.metron.stellar.dsl.MapVariableResolver; |
| import org.apache.metron.stellar.dsl.StellarFunctions; |
| import org.apache.metron.stellar.dsl.VariableResolver; |
| import org.apache.metron.stellar.common.utils.ConversionUtils; |
| |
| import java.io.Serializable; |
| import java.util.HashMap; |
| import java.util.Map; |
| |
| /** |
| * The default implementation of a StellarStatefulExecutor. |
| */ |
| public class DefaultStellarStatefulExecutor implements StellarStatefulExecutor, Serializable { |
| |
| /** |
| * The current state of the Stellar execution environment. |
| */ |
| private Map<String, Object> state; |
| |
| /** |
| * Provides additional context for initializing certain Stellar functions. For |
| * example, references to Zookeeper or HBase. |
| */ |
| private Context context; |
| |
| /** |
| * Responsible for function resolution. |
| */ |
| private FunctionResolver functionResolver; |
| |
| public DefaultStellarStatefulExecutor() { |
| this(StellarFunctions.FUNCTION_RESOLVER(), Context.EMPTY_CONTEXT()); |
| } |
| |
| public DefaultStellarStatefulExecutor(FunctionResolver functionResolver, Context context) { |
| clearState(); |
| this.context = context; |
| this.functionResolver = functionResolver; |
| } |
| |
| /** |
| * @param initialState Initial state loaded into the execution environment. |
| */ |
| public DefaultStellarStatefulExecutor(Map<String, Object> initialState) { |
| this(); |
| this.state = new HashMap<>(initialState); |
| } |
| |
| /** |
| * The current state of the Stellar execution environment. |
| */ |
| @Override |
| public Map<String, Object> getState() { |
| return ImmutableMap.copyOf(state); |
| } |
| |
| /** |
| * Execute an expression and assign the result to a variable. The variable is maintained |
| * in the context of this executor and is available to all subsequent expressions. |
| * |
| * @param variable The name of the variable to assign to. |
| * @param expression The expression to execute. |
| * @param transientState Additional state available to the expression. This most often represents |
| * the values available to the expression from an individual message. The state |
| * maps a variable name to a variable's value. |
| */ |
| @Override |
| public void assign(String variable, String expression, Map<String, Object> transientState) { |
| Object result = execute(expression, transientState); |
| if(result == null || variable == null) { |
| return; |
| } |
| state.put(variable, result); |
| } |
| |
| @Override |
| public void assign(String variable, Object value) { |
| if(value == null || variable == null) { |
| return; |
| } |
| state.put(variable, value); |
| } |
| |
| /** |
| * Execute a Stellar expression and return the result. The internal state of the executor |
| * is not modified. |
| * |
| * @param expression The expression to execute. |
| * @param state Additional state available to the expression. This most often represents |
| * the values available to the expression from an individual message. The state |
| * maps a variable name to a variable's value. |
| * @param clazz The expected type of the expression's result. |
| * @param <T> The expected type of the expression's result. |
| */ |
| @Override |
| public <T> T execute(String expression, Map<String, Object> state, Class<T> clazz) { |
| Object resultObject = execute(expression, state); |
| |
| // perform type conversion, if necessary |
| T result = ConversionUtils.convert(resultObject, clazz); |
| if (result == null) { |
| throw new IllegalArgumentException(String.format("Unexpected type: expected=%s, actual=%s, expression=%s", |
| clazz.getSimpleName(), ClassUtils.getShortClassName(resultObject,"null"), expression)); |
| } |
| |
| return result; |
| } |
| |
| @Override |
| public void clearState() { |
| this.state = new HashMap<>(); |
| } |
| |
| @Override |
| public void setContext(Context context) { |
| this.context = context; |
| } |
| |
| public void setFunctionResolver(FunctionResolver functionResolver) { |
| this.functionResolver = functionResolver; |
| } |
| |
| /** |
| * Execute a Stellar expression. |
| * |
| * @param expression The expression to execute. |
| * @param transientState Additional state available to the expression. This most often represents |
| * the values available to the expression from an individual message. The state |
| * maps a variable name to a variable's value. |
| */ |
| private Object execute(String expression, Map<String, Object> transientState) { |
| VariableResolver variableResolver = new MapVariableResolver(state, transientState); |
| StellarProcessor processor = new StellarProcessor(); |
| return processor.parse(expression, variableResolver, functionResolver, context); |
| } |
| } |