Getting error when mapping PostgreSQL LTREE column in hibernate

问题

I am trying to map postgresql ltree column in hibernate as follows:

In entity :

private String path;

@Column(name="org_path", columnDefinition="ltree")
public String getPath() {
   return path;

Table structure:

CREATE TABLE relationship (
    relationship_id int4 NOT NULL,
    parent_organization_id uuid NOT NULL,
    child_organization_id uuid NOT NULL,
    org_path ltree NOT NULL,
    CONSTRAINT relationship_pk PRIMARY KEY (relationship_id),
    CONSTRAINT organization_fk3 FOREIGN KEY (parent_organization_id) REFERENCES organization(organization_id) ON DELETE RESTRICT ON UPDATE RESTRICT,
    CONSTRAINT organization_fk4 FOREIGN KEY (child_organization_id) REFERENCES  organization(organization_id) ON DELETE RESTRICT ON UPDATE RESTRICT
)

Getting the following error:

wrong column type encountered in column [org_path] in table [relationship]; found [“schemaName"."ltree" (Types#OTHER)], but expecting [ltree (Types#VARCHAR)]

Can anyone help how to resolve this issue?

回答1:

Implement a custom LTreeType class in Java as follows:

public class LTreeType implements UserType {

    @Override
    public int[] sqlTypes() {
        return  new int[] {Types.OTHER};
    }

    @SuppressWarnings("rawtypes")
    @Override
    public Class returnedClass() {
        return String.class;
    }

    @Override
    public boolean equals(Object x, Object y) throws HibernateException {
        return x.equals(y);
    }

    @Override
    public int hashCode(Object x) throws HibernateException {
        return x.hashCode();
    }

    @Override
    public Object nullSafeGet(ResultSet rs, String[] names, Object owner)
            throws HibernateException, SQLException {
        return rs.getString(names[0]);
    }

    @Override
    public void nullSafeSet(PreparedStatement st, Object value, int index)
            throws HibernateException, SQLException {
        st.setObject(index, value, Types.OTHER);
    }

    @Override
    public Object deepCopy(Object value) throws HibernateException {
        return new String((String)value);
    }

    @Override
    public boolean isMutable() {
        return false;
    }

    @Override
    public Serializable disassemble(Object value) throws HibernateException {
        return (Serializable)value;
    }

    @Override
    public Object assemble(Serializable cached, Object owner)
            throws HibernateException {
        return cached;
    }

    @Override
    public Object replace(Object original, Object target, Object owner)
            throws HibernateException {
        // TODO Auto-generated method stub
        return deepCopy(original);
    }

}

And annotate the Entity class as follows:

    @Column(name = "path", nullable = false, columnDefinition = "ltree")
    @Type(type = "LTreeType")
    private String path;

回答2:

I had fits until I also created an LQueryType just like the class @arnabbiswas provided for LTreeType. My code only knows about Strings, but Postgres does not know how to use ltree with Strings. The types and operations are:

ltree ~ lquery
ltree @> ltree

So my Kotlin JPA is like this:

val descendantIds = treeRepo.findAllDescendantIds("*.$id.*{1,}")
. . .
@Query(
    "SELECT node_id FROM tree WHERE path ~ CAST(:idQuery AS lquery);"
    , nativeQuery = true)
fun findAllDescendantIds(@Param("idQuery") idQuery: String): Array<Long>

回答3:

just add this modifications on @anarbbswas code and then it will work fine

 @Override
public Object nullSafeGet(ResultSet rs, String[] names,SharedSessionContractImplementor session, Object owner)
        throws HibernateException, SQLException {
    return rs.getString(names[0]);
}

@Override
public void nullSafeSet(PreparedStatement st, Object value, int index, SharedSessionContractImplementor session) throws HibernateException, SQLException {
    st.setObject(index, value, Types.OTHER);
}

@Override
public Object deepCopy(Object value) throws HibernateException {
    if (value == null)
        return null;
    if (! (value instanceof String))
        throw new IllegalStateException("Expected String, but got: " + value.getClass());
    return value;
}

来源：https://stackoverflow.com/questions/41287897/getting-error-when-mapping-postgresql-ltree-column-in-hibernate