expression.java

一个java生成自动生成Excel

package net.sf.jxls.parser;

import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import net.sf.jxls.transformer.Configuration;

import org.apache.commons.beanutils.PropertyUtils;
import org.apache.commons.jexl.ExpressionFactory;
import org.apache.commons.jexl.JexlContext;
import org.apache.commons.jexl.JexlHelper;


/**
 * Represents JEXL expression
 * @author Leonid Vysochyn
 */
public class Expression {
    String expression;
    String rawExpression;
    String aggregateFunction;
    String aggregateField;
    Map beans;
    List properties = new ArrayList();
    org.apache.commons.jexl.Expression jexlExpresssion;

    Configuration config;

    Property collectionProperty;

    public Property getCollectionProperty() {
        return collectionProperty;
    }

    public List getProperties() {
        return properties;
    }

    public String getExpression() {
        return expression;
        
    }

    public Expression(String expression, Configuration config) {
        this.expression = expression;
        this.config = config;
    }

    public Expression(String expression, Map beans, Configuration config) throws Exception {
        this.config = config;
        this.expression = expression;
        this.rawExpression = parseAggregate(expression);
        this.beans = beans;
        jexlExpresssion = ExpressionFactory.createExpression( rawExpression );
        parse();
    }

    public Object evaluate() throws Exception {
        if (beans != null && !beans.isEmpty()){
            JexlContext context = JexlHelper.createContext();
            context.setVars(beans);
            Object ret = jexlExpresssion.evaluate(context);
            if (aggregateFunction != null) {
            	return calculateAggregate(aggregateFunction, aggregateField, ret);
            }
            return ret;
        }
        return expression;
    }

    private String parseAggregate(String expression)
    {
    	int i = expression.indexOf(":");
    	if (i >= 0) {
    		String aggregate = expression.substring(0, i);
    		if (aggregate.length() == 0) {
    			aggregateFunction = null;
    			aggregateField = null;
    		}
    		else {
    			int f1 = aggregate.indexOf("(");
    			int f2 = aggregate.indexOf(")");
    			if (f1 != -1 && f2 != -1 && f2 > f1) {
    				aggregateFunction = aggregate.substring(0, f1);
    				aggregateField = aggregate.substring(f1+1, f2);
    			}
    			else {
    				aggregateFunction = aggregate;
    				aggregateField = "c1";
    			}
    		}
    		return expression.substring(i+1);
    	}
        aggregateFunction = null;
        aggregateField = null;
        return expression;
    }
    
    private void parse() {
        Property prop = new Property(rawExpression, beans, config);
        this.properties = new ArrayList();
        this.properties.add(prop);
        if (prop.isCollection() && aggregateFunction == null && collectionProperty == null) {
            this.collectionProperty = prop;
        }
    }

    private Object calculateAggregate(String function, String field, Object list)
    {
    	Aggregator agg = Aggregator.getInstance(function);
    	if (agg != null) {
    		if (list instanceof Collection) {
	    		Collection coll = (Collection) list;
                for (Iterator iterator = coll.iterator(); iterator.hasNext();) {
                    Object o = iterator.next();
	    			try {
		    			Object f = PropertyUtils.getProperty(o, field);
		    			agg.add(f);
	    			}
	    			catch (InvocationTargetException e) {
	    				e.printStackTrace();
	    			}
	    			catch (NoSuchMethodException e) {
	    				e.printStackTrace();
	    			}
	    			catch (IllegalAccessException e) {
	    				e.printStackTrace();
	    			}
	    		}
    		}
    		else {
    			try {
    				Object f = PropertyUtils.getProperty(list, field);
    				agg.add(f);
    			}
    			catch (InvocationTargetException e) {
    				e.printStackTrace();
    			}
    			catch (NoSuchMethodException e) {
    				e.printStackTrace();
    			}
    			catch (IllegalAccessException e) {
    				e.printStackTrace();
    			}
    		}
    		return agg.getResult();
    	}
        return list;
    }
    
    public String toString() {
        return expression;
    }
}