Hibernate Mapping Types

In Hibernate we are mapping SQL data types to the Java data types. In this section we will see the available Hibernate Mapping Types and its corresponding Java Types.

Hibernate Mapping Types

Hibernate Mapping Types - Mapping between SQL and Hibernate Java objects

As you already know Hibernate is an ORM tool that retrieves the data from databases in the Java data types. So, you should be well aware of the SQL data types and its corresponding Java data types. With a solid understanding of Hibernate Mapping Types you will be able to write robust Hibernate based applications.

This tutorial is a Comprehensive Guide to understand Hibernate Mapping Types, where we will see all the SQL to Java mapping types for developing Hibernate based ORM layers. You will learn to correctly map SQL types to appropriate Java types in your Hibernate based ORM application.

In this post we are going to list the mapping between SQL Types to Hibernate (Java) Types. Hibernate Types is the actual Java type that is used in the Entity class for mapping table data to Java objects.

Hibernate Mapping Types

Importance of Hibernate ORM

Hibernate is a very popular and widely used Object-Relational Mapping (ORM) tool in Java programming language which is used to construct the data access layer for Java applications. This framework is feature rich and very efficient, which makes it an ideal framework for data based driven application development. Hibernate is database independent and supports all the major relational databases in the market. As a Java developer you must learn the Hibernate framework and master it by experimenting with the sample projects.

Understanding Hibernate Mapping Types

In Hibernate the Mapping Types are used to define the mapping between database field type (data type) to the equivalent Java types while writing the entity class. Based on this mapping information Hibernate converts the SQL data type to Java data types and builds entity objects. The command Java types used are String, int, Integer, double, Double, Date etc.

We can categorize these mapping types into following:

  1. Basic Types
  2. Temporal Types
  3. Boolean Type
  4. Binary Types
  5. Enumerations
  6. Custom Mapping Types

Lets see all these mapping types in detail.

Hibernate Mapping Types

1. Basic Types

  • StringType: SQL VARCHAR is mapped to String data type.
  • IntegerType, LongType, DoubleType: SQL numeric types are mapped to respective data types such as Long, Integer and Double.

2. Temporal Types

  • DateType, TimeType, TimestampType: Database fields types SQL DATE, TIME, and TIMESTAMP are mapped to Java java.util.Date.

3. Boolean Type

  • BooleanType: In we have to handle the Boolean data then then Java boolean data type is used and it is mapped to a database CHAR(1) or INTEGER, depending on the database.

4. Binary Types

  • BinaryType: If we have Binary data type such as BLOB in the database then it is mapped to Java byte array.

5. Enumerations

  • EnumType: If we have Java Enum type of data into database then it is mapped to a database VARCHAR or INTEGER.

6. Custom Mapping Types

Hibernate provides a wide range of built-in mapping types, but even if it is not meeting your requirements then you can go for Custom Mapping Types. The Custom Mapping Types can be developed by implementing the org.hibernate.usertype.UserType interface.

How to Use Mapping Types

There are two ways you can specify mapping in your Hibernate applications. These are:

  1. XML Mapping
  2. Annotation Mapping

Primitive Type Mapping in Hibernate

Here we will fist see the primitive Java types mapped to the SQL data types.

Sr No. Mapping Type Java Type ANSI SQL Type Description
1 Integer int or java.lang.Integer INTEGER Database INTEGER is mapped to int or Integer Java Type
2 long long or java.lang.Long BIGINT SQL BIGINT is mapped to long or java.lang.Long
3 short short or java.lang.Short SMALLINT SQL SMALLINT is mapped to short or java.lang.Short
4 float float or java.lang.Float FLOAT float or java.lang.Float
5 double double or java.lang.Double Double SQL Double is mapped to double or java.lang.Double
6 big_decimal java.math.BigDecimal NUMERIC SQL NUMERIC is mapped to java.math.BigDecimal
7 character java.lang.String CHAR(1) CHAR is mapped to Java java.lang.String
8 string java.lang.String VARCHAR VARCHAR is mapped to java.lang.String
9 byte byte or java.lang.Byte TINYINT TINYINT in SQL is mapped to byte or java.lang.Byte
10 boolean boolean or java.lang.Booleon BIT SQL BIT is mapped to boolean or java.lang.Booleon in Java
11 yes/no boolean or java.lang.Booleon CHAR(1) ('Y' or 'N') SQL CHAR is mapped to boolean or java.lang.Booleon in Java
12 true/false boolean or java.lang.Booleon CHAR(1) ('T' or 'F') SQL CHAR is mapped to boolean or java.lang.Booleon in Java Entity class

Date and Time Types

Now we will see how SQL Date and Time SQL types are mapped to Hibernate Entity class.

 

Sr. No. Mapping Type Java Type ANSI SQL Type Description
1 date java.util.Date or java.sql.Date DATE DATE is mapped to java.util.Date or java.sql.Date
2 DATE java.util.Date or java.sql.Time TIME TIME of SQL is mapped to java.util.Date or java.sql.Time
3 timestamp java.util.Date or java.sql.Timestamp TIMESTAMP If you have TIMESTAMP in SQL then you will map it to java.util.Date or java.sql.Timestamp Java classes.
4 calendar java.util.Calendar TIMESTAMP SQL TIMESTAMP is mapped to java.util.Calendar
5 calendar_date java.util.Calendar DATE DATE is mapped to java.util.Calendar

Binary and Large Object Types

Database table column types Binary and Large Object Types mappings are given below:

Sr . No. Mapping Type Java Type ANSI SQL Type Description
1 binary byte[] VARBINARY (or BLOB) SQL VARBINARY (or BLOB) is mapped to Java byte[] types.
2 text java.lang.String CLOB SQL CLOB should be mapped to java.lang.String
3 serializable any Java class that implements java.io.Serializable VARBINARY (or BLOB) The table column type VARBINARY (or BLOB) is mapped to any Java class that implements java.io.Serializable.
4 clob java.sql.Clob CLOB SQL CLOB should be mapped to java.sql.Clob
5 blob java.sql.Blob BLOB SQL BLOB will be mapped to Java java.sql.Blob

JDK-related Types

Now we will see the JDK related mapping types.

Sr. No. Mapping Type Java Type ANSI SQL Type Description
1 class java.lang.Class VARCHAR SQL VARCHAR should be mapped to java.lang.Class
2 locale java.util.Locale VARCHAR VARCHAR can also be mapped to java.util.Locale
3 timezone java.util.TimeZone VARCHAR VARCHAR column field can be mapped to java.util.TimeZone if the data is TimeZone data
4 currency java.util.Currency VARCHAR If you have currency data in table then you can map it to java.util.Currency
5 blob java.sql.Blob BLOB SQL BLOB should be mapped to java.sql.Blob

Summary

Hibernate comes with the predefined mapping types that you can use in your hibernate application to map your database column types to the Java Types. Hibernate also provides support for creating user-defined mapping types.
In this tutorial we have learned Hibernate Mapping Types in detail. You can check more tutorials at:

Tutorials

  1. Why hibernate is used?
  2. Hibernate Native SQL Example
  3. Hibernate Update Query
  4. Hibernate Delete Query
  5. Hibernate Count Query
  6. Writing First Hibernate Code
  7. Running First Hibernate 3.0 Example
  8. Hibernate Book
  9. Understanding Hibernate O/R Mapping
  10. Using Hibernate to generate id incrementally
  11. Hibernate Query Language
  12. Preparing table for HQL Examples
  13. Writing ORM for Insurance table
  14. HQL from clause Example
  15. Hibernate Select Clause
  16. HQL Where Clause Example
  17. Hibernate Architecture
  18. HQL Group By Clause Example
  19. hibernateTemplate-Order Results
  20. Hibernate Criteria Query Example
  21. Hibernate How To
  22. Hibernate Quickly
  23. Hibernate 3.1.2 Released
  24. HQL Order By Example
  25. Hibernate 3.1.3 Released
  26. Hibernate 3.1.1 Released
  27. Introduction to Hibernate 3.0
  28. Complete Hibernate 3.0 and Hibernate 4 Tutorial
  29. Hibernate Avg() Function (Aggregate Functions)
  30. Hibernate Max() Function (Aggregate Functions)
  31. Hibernate Min() Function (Aggregate Functions)
  32. Hibernate Criteria Expression (eq)
  33. Hibernate Criteria Expression (lt)
  34. Hibernate Criteria Expression (le)
  35. Hibernate Criteria Expression (gt)
  36. Hibernate Criteria Expression (ge)
  37. Hibernate Criteria Expression (and)
  38. Hibernate Criteria Expression (or)
  39. Hibernate Projections (rowCount or countDistinct)
  40. Hibernate Projection Count