MVEL自定义函数重复掉用报错：duplicate function

MVEL自定义表达式重复掉用报错：duplicate function

原因：第一次调用时会将function缓存，再次调用时提示函数重复

方案：先将funciton放入缓存，再次调用时直接调用声明缓存中的函数

• 自定义函数名，不要与参数名相同

示例代码：

@RunWith(SpringRunner.class)
@SpringBootTest
public class MvelTest {
        
    @Test
    public void evalTest(){
        //表达式
        String roundup = "def roundup(num) { roundnum = null; if(num != null){ int roundnum = Math.round(num); } return roundnum; }";
        VariableResolverFactory functionFactory = new MapVariableResolverFactory();
        MVEL.eval(roundup, functionFactory);

        VariableResolverFactory resolverFactory = new MapVariableResolverFactory();
        resolverFactory.setNextFactory(functionFactory);
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("A", new BigDecimal(2.33));
        map.put("B", new BigDecimal(4));
        String exp = "roundup(A*B)";
        System.out.println(MVEL.eval(exp, map, resolverFactory));

        System.out.println("------------");

        VariableResolverFactory resolverFactory2 = new MapVariableResolverFactory();
        resolverFactory2.setNextFactory(functionFactory);
        Map<String, Object> map2 = new HashMap<String, Object>();
        map2.put("A", new BigDecimal(3.33));
        map2.put("B", new BigDecimal(2));
        System.out.println(MVEL.eval(exp, map2, resolverFactory2));
    }
}

错误代码示例

向缓存中加入roundup函数

第一次执行成功

再次调用再次向缓存中加入roundup函数

VariableResolverFactory中存在函数抛出异常