Specification JPA query it and HQL, SQL queries

1、Specification

    
    
//查询条件List
List<Predicate> predicateList = new ArrayList<Predicate>();

Specification specification = new Specification() {
@Override
public Predicate toPredicate(Root root, CriteriaQuery criteriaQuery, CriteriaBuilder criteriaBuilder) {
//root即是Join<>内部第一个泛型的类型，意思就是用SkuProduct与Picture通过SkuProduct的pictures左联
Join<SkuProduct,Picture> skuProductPictureJoin = root.join( "pictures",JoinType.INNER);
//添加第1个查询条件：SkuProduct的code等于skuProduct.getCode()，然后将这个criteriaBuilder的条件添加到predicateList
predicateList.add(criteriaBuilder.equal(root.get( "code"),skuProduct.getCode()));
//添加第2个条件
predicateList.add(criteriaBuilder.notEqual(skuProductPictureJoin.get( "pictureType"), 0));
//返回
return criteriaBuilder.and(predicateList.toArray( new Predicate[predicateList.size()]));
}
};

// 重要说明：Specification不支持右连接！
//Specification specification = new Specification() {
// @Override
// public Predicate toPredicate(Root root, CriteriaQuery criteriaQuery, CriteriaBuilder criteriaBuilder) {
// Join<Picture,SkuProduct> skuProductPictureJoin = root.join("pictures",JoinType.RIGHT);
// predicateList.add(criteriaBuilder.notEqual(root.get("pictureType"),0));
// predicateList.add(criteriaBuilder.equal(skuProductPictureJoin.get("code"),skuProduct.getCode()));
// return criteriaBuilder.and(predicateList.toArray(new Predicate[predicateList.size()]));
// }
//};

List<SkuProduct> results = skuProductRepository.findAll(specification);
if(results!= null){
results.stream().forEach(result->{
System.out.println(result);
});
}
   
   

2, HQL

    
    
@Query(value = "SELECT p FROM Picture p WHERE p.code= :code")
List<Picture> findByPicture(@Param(value = "code") String code);
   
   

3、SQL

3.1 -: placeholder

    
    
@Query(value = "SELECT p.* FROM picture p LEFT JOIN sku_product_pictures sp_p ON p.id=sp_p.pictures_id LEFT JOIN sku_product sp ON sp_p.sku_product_id=sp.id WHERE sp.code= :code AND p.picture_type=0",nativeQuery = true)
List<Picture> findBySkuProductCodeAndPicture(@Param(value = "code") String code);
   
   

3.2 -? Placeholder

    
    
@Query(value = "SELECT p.* FROM picture p LEFT JOIN sku_product_pictures sp_p ON p.id=sp_p.pictures_id LEFT JOIN sku_product sp ON sp_p.sku_product_id=sp.id WHERE sp.code=?1 AND p.picture_type=?2",nativeQuery = true)
List<Picture> findSkuProductCodeAndPicture(String code,int pictureType);
   
   

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Original Address: https: //blog.csdn.net/trusause/article/details/78672595