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Custom type mapping

RedG allows you to customize the SQL to Java type mapping for the generated entity classes. When analysing a database schema, RedG always tries to find an appropriate Java datatype for a column. There are three cases, where this might not be enough:

• You want a different Java datatype that still represents the same database datatype (eg. long instead of BigDecimal for NUMBER(10))
• RedG cannot understand the semantic meaning of a column datatype (eg. NUMBER(1) or CHAR(1) for boolean)
• You want to plug in a custom, maybe even far more complex, data type and use it instead of the default types

If this happens, you can create a custom type mapping. The following sections describe how to specify your custom mapping.

JSON file

If you want to specify your mapping in a JSON file, use the JsonFileDataTypeProvider. The Maven plugin has built-in support for JSON files.

The syntax for the JSON file is simple: You can specify tableMappings that specify the type for a column inside a table or you can use the defaultMappings where you can assign a data type to be used for a specific SQL type. The tableMappings have a higher priority and can be used to override the defaultMappings.

For the tableMappings: Each table gets an own object. The key for that object is the full table name (including the schema name). This object contains a key for each column you want to map. The key is the column name. The value for each key is the wanted data type.

For the defaultMappings: The key is the SQL data type (with or without precision information), the value is the Java type. SQL types with precision information always take precedence over types without precision information. So when a column has the data type NUMBER(1) and the mappings contain both NUMBER -> Long and NUMBER(1) -> Boolean the column will be mapped to a Boolean type. When dealing with VARCHARs or similar, you can also use "precision" (aka length) information, but do not include CHAR inside the brackets (eg. if type is VARCHAR2(100 CHAR), use VARCHAR2(100) to match this).

Example:

{
  "tableMappings": {
    "SCHEMA-NAME.TABLE-NAME": {
      "COLUMN-NAME": "your.java.Datatype",
      "OTHER-COLUMN": "other.Type"
    },
    "SCHEMA-NAME.OTHER-TABLE": {
      "ID-COLUMN": "long"
    }
  },
  "defaultMappings": {
    "NUMBER": "java.lang.Long",
    "NUMBER(1)": "java.lang.Boolean"
  }
}

XML file

If you want to specify your type mapping with an XML file, use the XmlFileDataTypeProvider. The Maven plugin has built-in support for XML files.

The root element is <typeMappings>. This element has a child <tableTypeMappings>. Each table you want to specify the types for gets a <table> element with a name attribute specifying the table name. Each table element has <column> child elements. These elements have a name attribute and their value is the wanted data type.

The other allowed child element is <defaultTypeMappings>. It can have multiple <type> children with a sql attribute specifying the SQL data type (with precision support just like for JSON). The value of this node is the Java type that the SQL type should be mapped to.

Example:

<typeMappings>
   <tableTypeMappings>
       <table name="TABLE_NAME">
            <column name="COLUMN_NAME">java.lang.String</column>
       </table>
   </tableTypeMappings>
   <defaultTypeMappings>
       <type sql="DECIMAL(1)">java-lang.Boolean</type>
   </defaultTypeMappings>
</typeMappings>

Java API

Custom implementations have to implement the DataTypeProvider interface. The method getCanonicalDataTypeName gets called for each column in every table. The method has to return a fully qualified class name that should be used for that column.

public interface DataTypeProvider {
    String getCanonicalDataTypeName(Column column);
}

Source

DataTypeProvider.java DefaultDataTypeProvider.java json/JsonFileDataTypeProvider.java xml/XmlFileDataTypeProvider.java