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

current project used spring data jpa , spring boot, time found it's convinence until meet requirement, found hard deal. have buyer entity , supplier entity , middle entity(buyersupplier), if i'd search buyer phone or name or both or all, have supply many methods, 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 bad.and actually, business logic more complex, meantime want search buyer belong special supplier , maybe special status buyer. corresponding sql below:

select b.* buyer b, buyer_supplier bs b.id = bs.buyer_id , bs.supplier_id = 1 , bs.stauts = 'activated' , b.name '%foo%' , b.phone '%123%' 

and want build dynamic sql, below:

select b.* buyer b, buyer_supplier bs b.id = bs.buyer_id if(name != null)     , b.name '%foo%' if(phone!=null)     , b.phone '%123%' if(supplierid>0)     , b.supplier_id = 1 if(status!=null)     , bs.stauts = 'activated' 

could give me code sample or documents teach me how implement above target?

imo, still need write code if(phone!=null&&name!=null).but can enscape code,and write once. first, should know specification<t> support dynamic query well.just paste 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 can enscape specification<t>, put code if(phone!=null&&name!=null) in it. 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, use join                 if (fieldname.contains(".")) {                     string[] names = stringutils.split(fieldname, ".");                     expression = root.get(names[0]);                     (int = 1; < names.length; i++) {                         expression = expression.get(names[i]);                     }                 } else {                     expression = root.get(fieldname);                 }                 // 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 sample code if(phone!=null&&name!=null) in it.