[英]NullPointerException when using EntityManager and Criteria in Java
我创建了一个类,该类根据前端应用程序中填充的某些过滤器进行查询。 基本上有3个过滤器:“标题”,“ startDate”和“ endDate”。 这是我面临的问题:
当我单独发送标题而不带日期时,系统运行正常; 当我发送带有日期的标题时,系统可以正常工作,并正确返回对象列表。 当我发送不带标题的日期时,系统将引发NullPointerException。
public class RacRepositoryImpl implements RacRepositoryQuery {
@PersistenceContext
private EntityManager entityManager;
@Override
public List<Rac> filtrar(RacFilter racFilter) throws Exception {
CriteriaBuilder builder = entityManager.getCriteriaBuilder();
CriteriaQuery<Rac> query = builder.createQuery(Rac.class);
Root<Rac> from = query.from(Rac.class);
Predicate predicate = builder.and();
//title
if (racFilter.getTitulo() != null & racFilter.getTitulo().length() > 2) {
predicate = builder.and(predicate,
builder.like(from.<String>get("titulo"), "%"+racFilter.getTitulo()+"%"));
}
//startDate
if (racFilter.getDataInicial() != null) {
predicate = builder.and(predicate,
builder.greaterThanOrEqualTo(from.<Date>get("dataHora"), racFilter.getDataInicial()));
}
//finalDate
if (racFilter.getDataFinal() != null) {
predicate = builder.and(predicate,
builder.lessThanOrEqualTo(from.<Date>get("dataHora"), racFilter.getDataFinal()));
}
// here it throws the NullPointer exception when I don't send the title information
TypedQuery<Rac> typedQuery = entityManager.createQuery(
query.select(from )
.where( predicate )
);
try {
List<Rac> results = typedQuery.getResultList();
return results;
} catch (Exception e) {
throw new Exception("not found");
}
}
我没有发布其他类,因为我已经调试了并且该类的属性很好。 问题是当我不发送字段“ title”时,这意味着当它为空(不是必需的)时,查询不起作用
NullPointerException的来源很可能在这里:
//title
if (racFilter.getTitulo() != null & racFilter.getTitulo().length() > 2) {
请用“ &&”替换“&”,然后查看结果。
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