com.mulesoft.mql.impl.JoinPredicate.java Source code

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Here is the source code for com.mulesoft.mql.impl.JoinPredicate.java

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/*
 * $Id$
 * --------------------------------------------------------------------------------------
 * Copyright (c) MuleSoft, Inc.  All rights reserved.  http://www.mulesoft.com
 *
 * The software in this package is published under the terms of the CPAL v1.0
 * license, a copy of which has been included with this distribution in the
 * LICENSE.txt file.
 */
package com.mulesoft.mql.impl;

import com.mulesoft.mql.JoinBuilder;
import com.mulesoft.mql.QueryBuilder;

import java.io.Serializable;
import java.util.Map;

import org.apache.commons.collections.Predicate;
import org.mvel2.MVEL;

public class JoinPredicate implements Predicate {

    private final QueryBuilder queryBuilder;
    private Serializable compiledExpression;
    private JoinBuilder join;
    private Serializable onExpression;

    public JoinPredicate(QueryBuilder queryBuilder) {
        this.queryBuilder = queryBuilder;

        join = queryBuilder.getJoin();
        if (join.getOn() != null) {
            onExpression = MVEL.compileExpression(join.getOn());
        }
        compiledExpression = MVEL.compileExpression(join.getExpression());
    }

    public boolean evaluate(Object object) {
        Map<String, Object> vars = (Map<String, Object>) object;

        try {
            if (onExpression != null) {
                // Execute the on expression. Continue as long as it doesn't return 
                // null or false.
                Object result = MVEL.executeExpression(onExpression, vars);

                if (result == null || Boolean.FALSE.equals(result)) {
                    return false;
                }
            }
        } catch (RuntimeException e) {
            throw new RuntimeException(
                    "Could not execute expression " + join.getExpression() + " on context " + object, e);
        }

        try {
            // Execute the expression and shove the result back in as the context variable
            Object result = MVEL.executeExpression(compiledExpression, vars);

            vars.put(queryBuilder.getJoin().getAs(), result);
        } catch (RuntimeException e) {
            throw new RuntimeException(
                    "Could not execute expression " + join.getExpression() + " on context " + object, e);
        }

        return true;
    }

}