How to implement Spring Data Jpa Dynamic Query and Joint inquiry - spring-data-jpa

Question

Current project I used Spring data jpa and spring boot, most time I found it's very convinence until meet this requirement, I found hard to deal.
That is I have Buyer Entity and Supplier Entity and the middle Entity(BuyerSupplier), if I'd like to search Buyer by phone or name or both or all, I have to supply many methods, like below:
if(phone!=null&&name!=null)
List<Buyer> findByPhoneAndName(phone,name)
else if(phone!=null)
List<Buyer> findByPhone(phone)
else if(name!=null)
List<Buyer> findByName(name)
else
List<Buyer> findAll()
Obviously, above code is very bad.And actually, my business logic is more complex, meantime I want to search buyer belong to a special Supplier and maybe a special status buyer. Corresponding sql like below:
select b.* from buyer b, buyer_supplier bs
where b.id = bs.buyer_id
and bs.supplier_id = 1
and bs.stauts = 'Activated'
and b.name like '%foo%'
and b.phone like '%123%'
and I also want to build dynamic sql, like below:
select b.* from buyer b, buyer_supplier bs
where b.id = bs.buyer_id
if(name != null)
and b.name like '%foo%'
if(phone!=null)
and b.phone like '%123%'
if(supplierId>0)
and b.supplier_id = 1
if(status!=null)
and bs.stauts = 'Activated'
Could anyone give me some code sample or documents could teach me how to implement my above target?

Answer 1

IMO, you still need to write code like if(phone!=null&&name!=null).But you can enscape the code,and write once.
First, you should know the Specification<T> that support the dynamic query well.Just paste my code below.
Specification<Goods> spec = new Specification<Goods>() {
#Override
public Predicate toPredicate(Root<Goods> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
Predicate predicate = cb.conjunction();
if (goodsSearch.getGoodsClassId() != -1) {
predicate = cb.and(predicate, cb.equal(root.get("goodsClassId"), goodsSearch.getGoodsClassId()));
}
return query.where(predicate).getRestriction();
}
};
return goodsDao.findAll(spec, pageable);
ok,you can use lambda instead of anonymous class.Then you can just enscape the Specification<T>, put the code like if(phone!=null&&name!=null) in it.
the sample code:
public Specification<T> term(String fieldName, Operator operator, Object value) {
return new Specification<T>() {
#Override
public Predicate toPredicate(Root<T> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder builder) {
if (value == null) {
return null;
}
Path expression = null;
// if a.b, then use join
if (fieldName.contains(".")) {
String[] names = StringUtils.split(fieldName, ".");
expression = root.get(names[0]);
for (int i = 1; i < names.length; i++) {
expression = expression.get(names[i]);
}
} else {
expression = root.get(fieldName);
}
// the different operation
switch (operator) {
case EQ:
return builder.equal(expression, value);
case NE:
return builder.notEqual(expression, value);
case LT:
return builder.lessThan(expression, (Comparable) value);
case GT:
return builder.greaterThan(expression, (Comparable) value);
case LIKE:
return builder.like((Expression<String>) expression, "%" + value + "%");
case LTE:
return builder.lessThanOrEqualTo(expression, (Comparable) value);
case GTE:
return builder.greaterThanOrEqualTo(expression, (Comparable) value);
case BT:
List<Object> paramList = (List<Object>) value;
if (paramList.size() == 2) {
return builder.between(expression, (Comparable) paramList.get(0), (Comparable) paramList.get(1));
}
case IN:
return builder.in(expression).value(value);
default:
return null;
}
}
};
}
I did not write the sample code if(phone!=null&&name!=null) in it.