INT-3054: Add ExpressionEvalMap Support
Use an immutable Map wrapper to evaluate expressions only when accessed. Polishing
This commit is contained in:
Artem Bilan
committed by
Gary Russell
Gary Russell
parent
3369d3f9b1
commit
56812d3861
@@ -0,0 +1,306 @@
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/*
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* Copyright 2013 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.integration.expression;
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import java.util.AbstractMap;
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import java.util.Collection;
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import java.util.Map;
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import java.util.Set;
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import org.springframework.expression.EvaluationContext;
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import org.springframework.expression.Expression;
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/**
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* <p>
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* An immutable {@link AbstractMap} implementation that wraps a Map<String, Expression>
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* and evaluates an {@code expression} for the provided {@code key} from the underlying
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* {@code original} Map.
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* </p>
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* <p>
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* Any mutating operations ({@link #put(String, Object)}, {@link #remove(Object)} etc.)
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* are not allowed on instances of this class. Mutation can be performed on underlying Map
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* if it supports it.
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* </p>
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* <p>
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* A {@link ExpressionEvalMapBuilder} must be used to instantiate this class
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* via its {@link #from(Map)} method:
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* {@code
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* ExpressionEvalMap evalMap = ExpressionEvalMap
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* .from(expressions)
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.usingCallback(new EvaluationCallback() {
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Object evaluate(Expression expression) {
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// return some expression evaluation
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}
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})
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.build();
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* }
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* </p>
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* <p>
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* Thread-safety depends on the original underlying Map.
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* Objects of this class are not serializable.
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* </p>
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*
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* @author Artem Bilan
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* @since 3.0
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*/
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public final class ExpressionEvalMap extends AbstractMap<String, Object> {
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public static final EvaluationCallback SIMPLE_CALLBACK = new EvaluationCallback() {
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@Override
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public Object evaluate(Expression expression) {
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return expression.getValue();
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}
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};
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private final Map<String, Expression> original;
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private final EvaluationCallback evaluationCallback;
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private ExpressionEvalMap(Map<String, Expression> original, EvaluationCallback evaluationCallback) {
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this.original = original;
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this.evaluationCallback = evaluationCallback;
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}
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/**
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* Gets the {@code value}({@link Expression}) for the provided {@code key}
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* from {@link #original} and returns the result of evaluation using {@link #evaluationCallback}.
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*/
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@Override
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public Object get(Object key) {
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Expression expression = original.get(key);
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if (expression != null) {
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return this.evaluationCallback.evaluate(expression);
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}
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return null;
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}
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@Override
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public Collection<Object> values() {
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throw new UnsupportedOperationException();
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}
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@Override
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public boolean containsKey(Object key) {
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return original.containsKey(key);
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}
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@Override
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public Set<String> keySet() {
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return original.keySet();
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}
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@Override
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public boolean isEmpty() {
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return original.isEmpty();
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}
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@Override
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public int size() {
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return original.size();
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}
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@Override
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public boolean equals(Object o) {
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return original.equals(o);
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}
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@Override
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public int hashCode() {
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return original.hashCode();
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}
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@Override
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public Set<Map.Entry<String, Object>> entrySet() {
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throw new UnsupportedOperationException();
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}
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@Override
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public Object put(String key, Object value) {
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throw new UnsupportedOperationException();
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}
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@Override
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public void putAll(Map<? extends String, ? extends Object> m) {
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throw new UnsupportedOperationException();
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}
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@Override
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public void clear() {
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throw new UnsupportedOperationException();
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}
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@Override
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public boolean containsValue(Object value) {
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throw new UnsupportedOperationException();
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}
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@Override
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public Object remove(Object key) {
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throw new UnsupportedOperationException();
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}
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public static ExpressionEvalMapBuilder from(Map<String, Expression> expressions) {
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return new ExpressionEvalMapBuilder(expressions);
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}
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/**
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* Implementations of this interface can be provided to build 'on demand {@link #get(Object)} logic'
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* for {@link ExpressionEvalMap}.
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*/
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public interface EvaluationCallback {
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Object evaluate(Expression expression);
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}
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/**
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* The {@link EvaluationCallback} implementation which evaluates an expression using
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* the provided {@code context}, {@code root} and {@code returnType} variables.
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*/
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public static class ComponentsEvaluationCallback implements EvaluationCallback {
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private final EvaluationContext context;
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private final Object root;
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private final Class<?> returnType;
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public ComponentsEvaluationCallback(EvaluationContext context, Object root, Class<?> returnType) {
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this.context = context;
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this.root = root;
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this.returnType = returnType;
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}
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@Override
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public Object evaluate(Expression expression) {
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if (this.context != null) {
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return expression.getValue(this.context, this.root, this.returnType);
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}
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return expression.getValue(this.root, this.returnType);
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}
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}
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/**
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* The builder class to instantiate {@link ExpressionEvalMap}.
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*/
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public static final class ExpressionEvalMapBuilder {
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private final Map<String, Expression> expressions;
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private EvaluationCallback evaluationCallback;
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private EvaluationContext context;
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private Object root;
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private Class<?> returnType;
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private final ExpressionEvalMapComponentsBuilder evalMapComponentsBuilder = new ExpressionEvalMapComponentsBuilderImpl();
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private final ExpressionEvalMapFinalBuilder finalBuilder = new ExpressionEvalMapFinalBuilderImpl();
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private ExpressionEvalMapBuilder(Map<String, Expression> expressions) {
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this.expressions = expressions;
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}
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public ExpressionEvalMapFinalBuilder usingCallback(EvaluationCallback callback) {
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this.evaluationCallback = callback;
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return finalBuilder;
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}
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public ExpressionEvalMapFinalBuilder usingSimpleCallback() {
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return this.usingCallback(SIMPLE_CALLBACK);
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}
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public ExpressionEvalMapComponentsBuilder usingEvaluationContext(EvaluationContext context) {
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this.context = context;
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return this.evalMapComponentsBuilder;
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}
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public ExpressionEvalMapComponentsBuilder withRoot(Object root) {
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this.root = root;
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return this.evalMapComponentsBuilder;
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}
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public ExpressionEvalMapComponentsBuilder withReturnType(Class<?> returnType) {
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this.returnType = returnType;
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return this.evalMapComponentsBuilder;
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}
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private class ExpressionEvalMapFinalBuilderImpl implements ExpressionEvalMapFinalBuilder {
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@Override
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public ExpressionEvalMap build() {
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if (evaluationCallback != null) {
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return new ExpressionEvalMap(expressions, evaluationCallback);
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}
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return new ExpressionEvalMap(expressions, new ComponentsEvaluationCallback(context, root, returnType));
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}
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}
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private class ExpressionEvalMapComponentsBuilderImpl extends ExpressionEvalMapFinalBuilderImpl
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implements ExpressionEvalMapComponentsBuilder {
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@Override
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public ExpressionEvalMapComponentsBuilder usingEvaluationContext(EvaluationContext context) {
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return ExpressionEvalMapBuilder.this.usingEvaluationContext(context);
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}
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@Override
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public ExpressionEvalMapComponentsBuilder withRoot(Object root) {
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return ExpressionEvalMapBuilder.this.withRoot(root);
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}
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@Override
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public ExpressionEvalMapComponentsBuilder withReturnType(Class<?> returnType) {
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return ExpressionEvalMapBuilder.this.withReturnType(returnType);
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}
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}
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}
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public interface ExpressionEvalMapFinalBuilder {
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ExpressionEvalMap build();
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}
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public interface ExpressionEvalMapComponentsBuilder extends ExpressionEvalMapFinalBuilder {
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ExpressionEvalMapComponentsBuilder usingEvaluationContext(EvaluationContext context);
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ExpressionEvalMapComponentsBuilder withRoot(Object root);
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ExpressionEvalMapComponentsBuilder withReturnType(Class<?> returnType);
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}
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}
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