利用spring3 El 编写自已的 表达式工具类

public class ExpressionUtils {
	
	public static Object getValue(Object model, String expression){
		return getValue(model, expression, false);
	}
	
	public static Object getValue(Object model, String expression, boolean throwEx){
		StandardEvaluationContext context= new StandardEvaluationContext();
		context.setRootObject(model);
		PropertyAccessor accessor1 = new MapAccessor();
		PropertyAccessor accessor2 = new ReflectivePropertyAccessor();
		List<PropertyAccessor> propertyAccessors = new ArrayList<PropertyAccessor>();
		propertyAccessors.add(accessor1);
		propertyAccessors.add(accessor2);
		context.setPropertyAccessors(propertyAccessors);
		ExpressionParser parser = new SpelExpressionParser();
		Expression exp = parser.parseExpression(expression); 
		try{
			return exp.getValue(context);
		}catch(SpelEvaluationException e){
			if (throwEx){
				throw new RuntimeException(e.getMessage(), e);
			}else{
				return null;
			}
		}
	}
	
	public static void setValue(Object model, String expression, Object value){
		StandardEvaluationContext context= new StandardEvaluationContext();
		context.setRootObject(model);
		PropertyAccessor accessor1 = new MapAccessor();
		PropertyAccessor accessor2 = new ReflectivePropertyAccessor();
		List<PropertyAccessor> propertyAccessors = new ArrayList<PropertyAccessor>();
		propertyAccessors.add(accessor1);
		propertyAccessors.add(accessor2);
		context.setPropertyAccessors(propertyAccessors);
		ExpressionParser parser = new SpelExpressionParser();
		Expression exp = parser.parseExpression(expression);
		String[] expr = expression.split("\\.");
		Object nodeModel = model;//遍历时节点索引时的model
		for (int i=0; i<expr.length - 1; i++){
			if (expr[i].matches(".+\\[\\d+\\]$")){
				nodeModel = doListExpression(expr[i], nodeModel);
			}else{
				nodeModel = doMapExpression(expr[i], nodeModel);
			}
		}
		exp.setValue(context, value);
	}

	@SuppressWarnings("unchecked")
	private static Object doMapExpression(String expr, Object nodeModel) {
		//map
		Map map = (Map)ExpressionUtils.getValue(nodeModel, expr);
		if (map == null){
			map = new HashMap();
			ExpressionUtils.setValue(nodeModel, expr, map);
		}
		return map;
	}

	@SuppressWarnings("unchecked")
	private static Object doListExpression(String expr, Object nodeModel) {
		String property = expr.substring(0, expr.indexOf("["));
		int index = Integer.parseInt(expr.substring(expr.indexOf("[") + 1, expr.length() - 1));
		List list = (List)ExpressionUtils.getValue(nodeModel, property);
		if (list == null){
			list = new ArrayList();
			Map item = new HashMap();
			list.add(item);
			ExpressionUtils.setValue(nodeModel, property, list);
			
			return item;
		}else{
			Map item = null;
			if (index >= list.size()){
				item = new HashMap();
				list.add(index, item);
			}else{
				item = (Map)list.get(index);
			}
			
			return item;
		}
	}
	
}