AbstractGenerator is the base class for various DDL generator of specific DB and
handles following tasks:
Extract information from Mapping to Schema
Loop through the schema and provide a skeleton for DDL creation
AbstractGenerator will automatically extract necessary information for DDL
creation. That information is handled by Schema.
To create new generator for a DBMS, you should:
Overwrite this class to create new generator for a DBMS.
If the syntax of DBMS is different to standard DDL syntax, you should
overwrite SchemaObject (Table, Field, KeyGenerator, Index, ForeignKey,...) classes.
The class SchemaObjectFactory who handles the SchemaObject creation must
be overwritten.
You must overwrite the TypeMapper if mapping between JDBC types and
specific DBMS’s types is different among various DBMS.
The example bellow shows how to create a generator for DB2:
Generator for DB2
public class Db2Generator extends AbstractGenerator {
public Db2Generator(final String globConf, final String dbConf)
throws GeneratorException {
super(globConf, dbConf);
setTypeMapper(new Db2TypeMapper(getConf()));
}
}
TypeMapper for DB2
public final class Db2TypeMapper extends AbstractTypeMapper {
public Db2TypeMapper(final Configuration conf) {
super(conf);
}
protected void initialize(final Configuration conf) {
// numeric types
this.add(new NotSupportedType("bit"));
LOG.warn("Db2 does not support 'TINY' type, use SMALLINT instead.");
this.add(new NoParamType("tinyint", "SMALLINT"));
this.add(new NoParamType("smallint", "SMALLINT"));
this.add(new NoParamType("integer", "INTEGER"));
this.add(new NoParamType("bigint", "BIGINT"));
}
}
Field for DB2
public class Db2Field extends Field {
public Db2Field() {
super();
}
public String toDDL() throws GeneratorException {
StringBuffer buff = new StringBuffer();
buff.append(getName()).append(" ");
buff.append(getType().toDDL(this));
if (isIdentity()) {
buff.append(" NOT NULL");
}
KeyGenerator keyGen = getKeyGenerator();
if (keyGen != null && isIdentity()) {
if (KeyGenerator.IDENTITY_KEY.equalsIgnoreCase(keyGen.getName())) {
buff.append(" GENERATED BY DEFAULT AS IDENTITY ").
append("START WITH 1 INCREMENT BY 1");
}
}
return buff.toString();
}
}
Field for DB2
public class Db2SchemaFactory extends SchemaFactory {
public Db2SchemaFactory() {
super();
}
public Field createField() {
return new Db2Field();
}
}
The GeneratorFactory class handles the specific database generator creation.
For example:
Generator generator = GeneratorFactory.
createDDLGenerator(“mysql”, “ddl.properties”, “mysql.properties”);
And to generate DDL, it should specify the printer and call generateDDL method.
generator.setPrinter(System.out);
Mapping mapping = new Mapping();
mapping.loadMapping("mapping.xml");
generator.generateDDL(mapping);
createForeignKeyDDL
protected final void createForeignKeyDDL(Table table,
DDLWriter writer)
throws GeneratorException
Generate DDL for foreign key.
table
- Table to generate DDL of foreign key for.writer
- DDLWriter to write schema objects to.
createIndex
public final void createIndex(Table table,
DDLWriter writer)
throws GeneratorException
Generate DDL for indices of given table.
table
- Table to generate DDL of indices for.writer
- DDLWriter to write schema objects to.
createSchema
public final void createSchema()
throws GeneratorException
Extracting informations from mapping to schema, this is done by 3 steps.
- Create key generators
- Create tables
- Create additional tables for many-many relations
generateCreate
public final void generateCreate(DDLWriter writer)
throws GeneratorException
Generate DDL for create statementof table.
CREATE TABLE prod (
id INTEGER NOT NULL,
name CHAR(16)
);
CREATE TABLE prod_detail (
id INTEGER NOT NULL,
prod_id CHAR(16)
);
writer
- DDLWriter to write schema objects to.
generateDrop
public final void generateDrop(DDLWriter writer)
throws GeneratorException
Generate DDL for drop statement of table.
writer
- DDLWriter to write schema objects to.
generateForeignKey
public final void generateForeignKey(DDLWriter writer)
throws GeneratorException
Generate DDL for foreign keys.
ALTER TABLE `prod_group` ADD CONSTRAINT `FK_prod_group_1`
FOREIGN KEY `FK_prod_group_1` (`id`, `name`)
REFERENCES `category` (`id`, `name`)
ON DELETE SET NULL
ON UPDATE CASCADE;
writer
- DDLWriter to write schema objects to.
generateHeader
public abstract void generateHeader(DDLWriter writer)
Generate header comment.
writer
- DDLWriter to write schema objects to.
generateIndex
public final void generateIndex(DDLWriter writer)
throws GeneratorException
Generate DDL for indices.
writer
- DDLWriter to write schema objects to.
generateKeyGenerator
public final void generateKeyGenerator(DDLWriter writer)
throws GeneratorException
Generate DDL for key generators (sequence/trigger).
writer
- DDLWriter to write schema objects to.
generatePrimaryKey
public final void generatePrimaryKey(DDLWriter writer)
throws GeneratorException
Generate DDL for primany keys.
writer
- DDLWriter to write schema objects to.
getConfiguration
public final DDLGenConfiguration getConfiguration()
Get configuration of generator.
- Configuration of generator.
getMapping
public final Mapping getMapping()
Get mapping document.
getMappingHelper
public final MappingHelper getMappingHelper()
Get mapping helper.
getSchema
public final Schema getSchema()
Get schema.
getSchemaFactory
public final SchemaFactory getSchemaFactory()
Get schema factory.
getTypeMapper
public final TypeMapper getTypeMapper()
Get type mapper.
setMapping
public final void setMapping(Mapping mapping)
Set mapping document.
- setMapping in interface Generator
mapping
- Mapping document.
setMappingHelper
protected final void setMappingHelper(MappingHelper mappingHelper)
Set mapping helper.
mappingHelper
- Mapping helper.
setSchemaFactory
protected final void setSchemaFactory(SchemaFactory schemaFactory)
Set schema factory.
schemaFactory
- Schema factory.
setTypeMapper
public final void setTypeMapper(TypeMapper typeMapper)
Set type mapper.
typeMapper
- Type mapper.