package org.ccframe.commons.jpaquery;

import java.util.ArrayList;
import java.util.List;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import org.springframework.data.jpa.domain.Specification;

/** 
 * 定义一个查询条件容器 
 * @author Jim
 */  
public class Criteria<T> implements Specification<T>{
	/**
	 * 
	 */
	private static final long serialVersionUID = 7723262888497747481L;

	private List<Criterion> criterionList = new ArrayList<Criterion>();
	
    public Criteria(){};
	
	public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder builder) {  
		if (!criterionList.isEmpty()) {
            List<Predicate> predicates = new ArrayList<Predicate>();  
            for(Criterion c : criterionList){  
                predicates.add(c.toPredicate(root, query,builder));  
            }  
            // 将所有条件用 and 联合起来  
            if (predicates.size() > 0) {  
                return builder.and(predicates.toArray(new Predicate[predicates.size()]));  
            }  
        }  
        return builder.conjunction();  
    }

	/** 
     * 增加简单条件表达式 
     */  
    public Criteria<T> add(Criterion criterion){  
        if(criterion!=null){  
            criterionList.add(criterion);  
        }
        return this;
    }
}