Problems in JOIN using Hibernate

Question

I'm beginner in Hibernate in JAVA and do not know how to solve this problem

I have two tables: Usuario and Certificado, and i want to create a relationship and theirs.

Class Certificado:

@Entity
@Table(name = "Certificado",
       uniqueConstraints = { @UniqueConstraint( columnNames = { "identifierUnique", "handleUser" } ) } )
public class Certificado {
    @Id
    @GenericGenerator(name="generator", strategy="increment")
    @GeneratedValue(generator="generator")
    private int handle;
    @Column(length = 255)
    @Column
    private int handleUser;

    @ManyToOne
    @JoinColumn(name="handle_user", referencedColumnName="handle")
    private Usuario usuario;
}

Class Usuario:

@Entity
@Table(name = "Usuario")
public class Usuario {
    @Id
    @GenericGenerator(name="generator", strategy="increment")
    @GeneratedValue(generator="generator")
    private int handle;
    @Column(length = 255, unique = true)
    private String email;   
    @Column(length = 20)
    private String password;    
    @OneToMany(mappedBy="usuario", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private Set<Certificado> certificados;

        ...
}

When I Execute a SQL function:

public static List<Object[]> loadCertificado30DaysBeforeExperation() throws Exception{      
        Session.begin();
        try {
            try {
                String select = "SELECT c FROM Certificado c "
                    + "LEFT JOIN c.handleUser AS user";
                return Session.list(select);
            } catch (Exception e) {
                throw e;
            }
        } finally {
            Session.commit();
        }
    }

Error:

   java.lang.NullPointerException

StackTrace:

java.lang.NullPointerException
    at org.hibernate.hql.internal.ast.HqlSqlWalker.createFromJoinElement(HqlSqlWalker.java:393)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.joinElement(HqlSqlBaseWalker.java:3645)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElement(HqlSqlBaseWalker.java:3431)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElementList(HqlSqlBaseWalker.java:3309)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromClause(HqlSqlBaseWalker.java:706)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:562)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:299)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:247)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:249)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:184)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:137)
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:105)
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:80)
    at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:168)
    at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:221)
    at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:199)
    at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1778)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:352)
    at com.sun.proxy.$Proxy15.createQuery(Unknown Source)
    at br.com.persistence.Session.list(Session.java:96)
    at br.com.utils.ServletUtils.loadCertificado30DaysBeforeExperation(ServletUtils.java:134)
    at br.com.monitoramento.MonitorThread.run(MonitorThread.java:25)

Community · Accepted Answer · 2017-05-23 11:57:06Z

2

Hibernate's HQL does not support intervals (and generally has extremely poor date maths support).

You'll need to use native SQL, or express the query without interval by doing the date calculations locally on the Java side.

Or you can register a user-defined SQL function and create a PostgreSQL function that does the date maths you want.

See:

and many more.

edited May 23, 2017 at 11:57

CommunityBot

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answered Mar 21, 2014 at 13:11

Craig Ringer

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1 Comment

fymoribe Over a year ago

i changed sql and occurred another error: NullPointerException.

sergiu · Accepted Answer · 2014-03-21 12:18:14Z

0

Have you tried removing the '' from '30' -> interval 30 days. Or escape the '30' -> \'30\'.

answered Mar 21, 2014 at 12:18

sergiu

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