proper hibernate annotation for byte

Question

I have an application using hibernate 3 1 and JPA annotations   It has a few objects with byte   attributes  1k - 200k in size    It uses the JPA  Lob annotation  and hibernate 3 1 can read these just fine on all major databases -- it seems to hide the JDBC Blob vendor peculiarities  as it should do     Entity public class ConfigAttribute      Lob   public byte   getValueBuffer         return m valueBuffer          We had to upgrade to 3 5  when we discovered that hibernate 3 5  breaks  and won t fix  this annotation combination in postgresql  with no workaround    I have not found a clear fix so far  but I did notice that if I just remove the  Lob  it uses the postgresql type bytea  which works  but only on postgres    annotation                   postgres     oracle      works on ------------------------------------------------------------- byte      Lob                oid          blob        oracle byte                         bytea        raw 255     postgresql byte      Type PBA           oid          blob        oracle byte      Type BT            bytea        blob        postgresql  once you use  Type   Lob seems to not be relevant note  oracle seems to have deprecated the  raw  type since 8i    I am looking for a way to have a single annotated class  with a blob property  which is portable across major databases    What is the portable way to annotate a byte   property  Is this fixed in some recent version of hibernate    Update  After reading this blog I have finally figured out what the original workaround in the JIRA issue was  Apparently you are supposed to drop  Lob and annotate the property as    Type type  org hibernate type PrimitiveByteArrayBlobType    byte   getValueBuffer          However  this does not work for me -- I still get OIDs instead of bytea  it did however work for the author of the JIRA issue  who seemed to want oid   After the answer from A  Garcia  I then tried this combo  which actually does work on postgresql  but not on oracle    Type type  org hibernate type BinaryType    byte   getValueBuffer          What I really need to do is control which  org hibernate annotations Type the combination   Lob   byte   gets mapped  to  on postgresql      Here is the snippet from 3 5 5 Final from MaterializedBlobType  sql type Blob    According to Steve s blog  postgresql wants you to use Streams for bytea  don t ask me why  and postgresql s custom Blob type for oids   Note also that using setBytes   on JDBC is also for bytea  from past experience    So this explains why use-streams has no affect they both assume  bytea    public void set PreparedStatement st  Object value  int index     byte   internalValue   toInternalFormat  value     if   Environment useStreamsForBinary            use streams   true    st setBinaryStream  index       new ByteArrayInputStream  internalValue    internalValue length        else        use streams   false   st setBytes  index  internalValue           This results in   ERROR  column  signature  is of type oid but expression is of type bytea   Update The next logical question is   why not just change the table definitions manually to bytea  and keep the   Lob   byte      This does work  UNTIL you try to store a null byte     Which the postgreSQL driver thinks is an OID type expression and the column type is bytea -- this is because hibernate  rightly  calls JDBC setNull   instead of JDBC setBytes null  which PG driver expects    ERROR  column  signature  is of type bytea but expression is of type oid   The type system in hibernate is currently a  work in progress   according to 3 5 5 deprecation comment    In fact so much of the 3 5 5 code is deprecated  it is hard to know what to look at when sub-classing the PostgreSQLDialect      AFAKT  Types BLOB  oid  on postgresql should be mapped to some custom type which uses OID style JDBC access  i e  PostgresqlBlobType object and NOT MaterializedBlobType    I ve never actually successfully used Blobs with postgresql  but I do know that bytea just simply works as one   I would expect   I am currently looking at the BatchUpdateException -- its possible that the driver doesn t support batching       Great quote from 2004    To sum up my ramblings  I d say they we should wait for the JDBC driver to do LOBs properly before changing Hibernate    References    https   forum hibernate org viewtopic php p 2393203 https   forum hibernate org viewtopic php p 2435174 http   hibernate atlassian net browse HHH-4617 http   postgresql 1045698 n5 nabble com Migration-to-Hibernate-3-5-final-td2175339 html https   jira springframework org browse SPR-2318 https   forums hibernate org viewtopic php p 2203382 amp sid b526a17d9cf60a80f13d40cf8082aafd http   virgo47 wordpress com 2008 06 13 jpa-postgresql-and-bytea-vs-oid-type

User · Answer

Here goes what O reilly Enterprise JavaBeans  3 0 says     JDBC has special types for these very large objects  The java sql Blob type represents binary data  and java sql Clob represents character data    Here goes PostgreSQLDialect source code  public PostgreSQLDialect         super                registerColumnType Types VARBINARY   bytea                    Notice it maps java sql Types BLOB as oid              registerColumnType Types BLOB   oid        So what you can do  Override PostgreSQLDialect as follows  public class CustomPostgreSQLDialect extends PostgreSQLDialect        public CustomPostgreSQLDialect             super             registerColumnType Types BLOB   bytea              Now just define your custom dialect   lt property name  hibernate dialect  value  br com ar dialect CustomPostgreSQLDialect   gt    And use your portable JPA  Lob annotation   Lob public byte   getValueBuffer       UPDATE  Here has been extracted here     I have an application running in hibernate 3 3 2 and the applications works fine  with all blob fields using oid  byte   in java             Migrating to hibernate 3 5 all blob fields not work anymore  and the server log shows  ERROR org hibernate util JDBCExceptionReporter - ERROR  column is of type oid but expression is of type bytea   which can be explained here     This generaly is not bug in PG JDBC  but change of default implementation of Hibernate in 3 5 version  In my situation setting compatible property on connection   did not helped             Much more this what I saw in 3 5 - beta 2  and i do not know if this was fixed is Hibernate - without  Type annotation - will auto-create column of type oid  but will try to read this as bytea    Interesting is because when he maps Types BOLB as bytea  See CustomPostgreSQLDialect  He get     Could not execute JDBC batch update    when inserting or updating

User · Answer

i fixed My issue by adding the annotation of  Lob which will create the byte   in oracle as blob   but this annotation will create the field as oid which not work properly   To make byte   created as bytea i made customer Dialect for postgres as below   Public class PostgreSQLDialectCustom extends PostgreSQL82Dialect       public PostgreSQLDialectCustom             System out println  Init PostgreSQLDialectCustom            registerColumnType  Types BLOB   bytea                    Override     public SqlTypeDescriptor remapSqlTypeDescriptor SqlTypeDescriptor sqlTypeDescriptor        if  sqlTypeDescriptor getSqlType      java sql Types BLOB          return BinaryTypeDescriptor INSTANCE            return super remapSqlTypeDescriptor sqlTypeDescriptor            Also need to override parameter for the Dialect  spring jpa properties hibernate dialect com ntg common DBCompatibilityHelper PostgreSQLDialectCustom  more hint can be found her   https   dzone com articles postgres-and-oracle

User · Answer

I m using the Hibernate 4 2 7 SP1 with Postgres 9 3 and following works for me    Entity public class ConfigAttribute      Lob   public byte   getValueBuffer         return m valueBuffer          as Oracle has no trouble with that  and for Postgres I m using custom dialect   public class PostgreSQLDialectCustom extends PostgreSQL82Dialect         Override     public SqlTypeDescriptor remapSqlTypeDescriptor SqlTypeDescriptor sqlTypeDescriptor        if  sqlTypeDescriptor getSqlType      java sql Types BLOB          return BinaryTypeDescriptor INSTANCE            return super remapSqlTypeDescriptor sqlTypeDescriptor           the advantage of this solution I consider  that I can keep hibernate jars untouched   For more Postgres Oracle compatibility issues with Hibernate  see my blog post

User · Answer

What is the portable way to annotate a byte   property    It depends on what you want  JPA can persist a non annotated byte    From the JPA 2 0 spec       11 1 6 Basic Annotation      The Basic annotation is the simplest   type of mapping to a database column    The Basic annotation can be applied   to a persistent property or instance   variable of any of the following   types  Java primitive  types  wrappers   of the primitive types    java lang String    java math BigInteger    java math BigDecimal    java util Date    java util Calendar  java sql Date    java sql Time  java sql Timestamp    byte    Byte    char    Character    enums  and any other   type that implements Serializable    As described in Section 2 8  the use   of the Basic annotation is optional   for persistent fields and properties   of these types  If the Basic   annotation is not specified for such a   field or property  the default values   of the Basic annotation will apply    And Hibernate will map a it  by default  to a SQL VARBINARY  or a SQL LONGVARBINARY depending on the Column size   that PostgreSQL handles with a bytea   But if you want the byte   to be stored in a Large Object  you should use a  Lob  From the spec      11 1 24 Lob Annotation      A Lob annotation specifies that a   persistent property or field should be   persisted as a large object to a   database-supported large object type    Portable applications should use the   Lob annotation when mapping to a   database Lob type  The Lob annotation   may be used in conjunction with the   Basic annotation or with the   ElementCollection annotation when the   element collection value is of basic   type  A Lob may be either a binary or   character type  The Lob type is   inferred from the type of the   persistent field or property and    except for string and character types    defaults to Blob    And Hibernate will map it to a SQL BLOB that PostgreSQL handles with a oid       Is this fixed in some recent version of hibernate    Well  the problem is that I don t know what the problem is exactly  But I can at least say that nothing has changed since 3 5 0-Beta-2  which is where a changed has been introduced in the 3 5 x branch   But my understanding of issues like HHH-4876  HHH-4617 and of PostgreSQL and BLOBs  mentioned in the javadoc of the  PostgreSQLDialect  is that you are supposed to set the following property  hibernate jdbc use streams for binary false   if you want to use oid i e  byte   with  Lob  which is my understanding since VARBINARY is not what you want with Oracle   Did you try this   As an alternative  HHH-4876 suggests using the deprecated PrimitiveByteArrayBlobType to get the old behavior  pre Hibernate 3 5    References   JPA 2 0 Specification   Section 2 8  Mapping Defaults for Non-Relationship Fields or Properties  Section 11 1 6  Basic Annotation  Section 11 1 24  Lob Annotation     Resources   http   opensource atlassian com projects hibernate browse HHH-4876 http   opensource atlassian com projects hibernate browse HHH-4617 http   relation to Bloggers PostgreSQLAndBLOBs

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Thanks Justin  Pascal for guiding me to the right direction  I was also facing the same issue with Hibernate 3 5 3  Your research and pointers to the right classes had helped me identify the issue and do a fix   For the benefit for those who are still stuck with Hibernate 3 5 and using oid   byte      LoB combination  following is what I have done to fix the issue    I created a custom BlobType extending MaterializedBlobType and overriding the set and the get methods with the oid style access   public class CustomBlobType extends MaterializedBlobType    private static final String POSTGRESQL DIALECT   PostgreSQLDialect class getName            Currently set dialect      private String dialect   hibernateConfiguration getProperty Environment DIALECT           non-Javadoc      see org hibernate type AbstractBynaryType set java sql PreparedStatement  java lang Object  int       Override public void set PreparedStatement st  Object value  int index  throws HibernateException  SQLException       byte   internalValue   toInternalFormat value        if  POSTGRESQL DIALECT equals dialect             try      I had access to sessionFactory through a custom sessionFactory wrapper  st setBlob index  Hibernate createBlob internalValue  sessionFactory getCurrentSession                    catch  SystemException e                    throw new HibernateException e                           else               st setBytes index  internalValue                           non-Javadoc      see org hibernate type AbstractBynaryType get java sql ResultSet  java lang String       Override public Object get ResultSet rs  String name  throws HibernateException  SQLException       Blob blob   rs getBlob name       if  rs wasNull              return null            int length    int  blob length        return toExternalFormat blob getBytes 1  length             Register the CustomBlobType with Hibernate  Following is what i did to achieve that   hibernateConfiguration  new AnnotationConfiguration    Mappings mappings   hibernateConfiguration createMappings    mappings addTypeDef  materialized blob    x y z BlobType   null

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I have finally got this working   It expands on the solution from A  Garcia  however  since the problem lies in the hibernate type MaterializedBlob type just mapping Blob   bytea is not sufficient  we need a replacement for MaterializedBlobType which works with hibernates broken blob support   This implementation only works with bytea  but maybe the guy from the JIRA issue who wanted OID could contribute an OID implementation   Sadly replacing these types at runtime is a pain  since they should be part of the Dialect  If only this JIRA enhanement gets into 3 6 it would be possible   public class PostgresqlMateralizedBlobType extends AbstractSingleColumnStandardBasicType lt byte   gt     public static final PostgresqlMateralizedBlobType INSTANCE   new PostgresqlMateralizedBlobType      public PostgresqlMateralizedBlobType       super  PostgresqlBlobTypeDescriptor INSTANCE  PrimitiveByteArrayTypeDescriptor INSTANCE          public String getName        return  materialized blob           Much of this could probably be static  does getBinder   really need a new instance    but I don t really understand the hibernate internal so this is mostly copy   paste   modify   public class PostgresqlBlobTypeDescriptor extends BlobTypeDescriptor implements SqlTypeDescriptor     public static final BlobTypeDescriptor INSTANCE   new PostgresqlBlobTypeDescriptor       public  lt X gt  ValueBinder lt X gt  getBinder final JavaTypeDescriptor lt X gt  javaTypeDescriptor       return new PostgresqlBlobBinder lt X gt  javaTypeDescriptor  this         public  lt X gt  ValueExtractor lt X gt  getExtractor final JavaTypeDescriptor lt X gt  javaTypeDescriptor       return new BasicExtractor lt X gt   javaTypeDescriptor  this         protected X doExtract ResultSet rs  String name  WrapperOptions options  throws SQLException          return  X rs getBytes name                      public class PostgresqlBlobBinder lt J gt  implements ValueBinder lt J gt     private final JavaTypeDescriptor lt J gt  javaDescriptor   private final SqlTypeDescriptor sqlDescriptor    public PostgresqlBlobBinder JavaTypeDescriptor lt J gt  javaDescriptor  SqlTypeDescriptor sqlDescriptor       this javaDescriptor   javaDescriptor  this sqlDescriptor   sqlDescriptor             public final void bind PreparedStatement st  J value  int index  WrapperOptions options    throws SQLException     st setBytes index   byte   value

User · Answer

I got it work by overriding annotation with XML file for Postgres  Annotation is kept for Oracle  In my opinion  in this case it would be best we override the mapping of this trouble-some enity with xml mapping  We can override single   multiple entities with xml mapping  So we would use annotation for our mainly-supported database  and a xml file for each other database   Note  we just need to override one single class   so it is not a big deal  Read more from my example  Example to override annotation with XML

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On Postgres  Lob is breaking for byte   as it tries to save it as oid  and for String also same problem occurs  Below code is breaking on postgres which is working fine on oracle    Lob private String stringField    and    Lob private byte     someByteStream    In order to fix above on postgres have written below custom hibernate dialect   public class PostgreSQLDialectCustom extends PostgreSQL82Dialect   public PostgreSQLDialectCustom         super        registerColumnType Types BLOB   bytea         Override  public SqlTypeDescriptor remapSqlTypeDescriptor SqlTypeDescriptor sqlTypeDescriptor        if  Types CLOB    sqlTypeDescriptor getSqlType            return LongVarcharTypeDescriptor INSTANCE            return super remapSqlTypeDescriptor sqlTypeDescriptor           Now configure custom dialect in hibernate   hibernate dialect X Y Z PostgreSQLDialectCustom      X Y Z is package name    Now it working fine   NOTE- My Hibernate version - 5 2 8 Final        Postgres version- 9 6 3

[java] proper hibernate annotation for byte[]

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