通过实体反射实现CriteriaQuery并列条件查询

将实体反射之后获取查询字段的值，并添加到Predicate对象数组中

public Predicate getPredicateAnd(T entity, Root<T> root, CriteriaBuilder cb) throws IntrospectionException



        , InvocationTargetException, IllegalAccessException {

    try {

        //通过反射获取类型

Class<?> c = entity.getClass();

        //获取类的字段

Field[] fields = c.getDeclaredFields();

        List<Predicate> predicateList = new ArrayList();

        for (Field field : fields) {

            PropertyDescriptor pd = new PropertyDescriptor(field.getName(), c);

            //获得get方法

Method getMethod = pd.getReadMethod();

            //执行get方法返回一个Object

Object fieldVal = getMethod.invoke(entity);



            if (fieldVal != null && !fieldVal.equals(0)) {

                Path<String> path = root.get(field.getName());

                Predicate p = cb.equal(path, fieldVal);

                predicateList.add(p);

            }

        }

        return cb.and(predicateList.toArray(new Predicate[]{}));

    } catch (Exception e) {

        log.error(e.getMessage());

    }

    return null;

}

 

下面是使用方法，因返回类型为Predicate所以直接作为参数传入到CriteriaQuery<?>的where函数中

public T findOne(final T entity) {

        return getSpecDao().findOne(new Specification<T>() {

            @Override

            public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb) {      

                try {

                    query.where( getPredicateAnd(entity, root, cb));

                } catch (InvocationTargetException e) {

                    e.printStackTrace();

                } catch (IllegalAccessException e) {

                    e.printStackTrace();

                } catch (IntrospectionException e) {

                    e.printStackTrace();

                }

                return null;

            }

        });

    }