DropNotNullConstraintChange.java

package liquibase.change.core;

import liquibase.change.AbstractChange;
import liquibase.change.Change;
import liquibase.change.ChangeMetaData;
import liquibase.change.ColumnConfig;
import liquibase.database.Database;
import liquibase.database.core.SQLiteDatabase;
import liquibase.database.core.SQLiteDatabase.AlterTableVisitor;
import liquibase.database.structure.Index;
import liquibase.statement.SqlStatement;
import liquibase.statement.core.SetNullableStatement;
import liquibase.util.StringUtils;

import java.util.ArrayList;
import java.util.List;

/**
 * Drops a not-null constraint from an existing column.
 */
public class DropNotNullConstraintChange extends AbstractChange {

    private String schemaName;
    private String tableName;
    private String columnName;
    private String columnDataType;


    public DropNotNullConstraintChange() {
        super("dropNotNullConstraint", "Drop Not-Null Constraint", ChangeMetaData.PRIORITY_DEFAULT);
    }

    public String getSchemaName() {
        return schemaName;
    }

    public void setSchemaName(String schemaName) {
        this.schemaName = StringUtils.trimToNull(schemaName);
    }

    public String getTableName() {
        return tableName;
    }

    public void setTableName(String tableName) {
        this.tableName = tableName;
    }

    public String getColumnName() {
        return columnName;
    }

    public void setColumnName(String columnName) {
        this.columnName = columnName;
    }

    public String getColumnDataType() {
        return columnDataType;
    }

    public void setColumnDataType(String columnDataType) {
        this.columnDataType = columnDataType;
    }

    public SqlStatement[] generateStatements(Database database) {
    	
//todo    	if (database instanceof SQLiteDatabase) {
//    		// return special statements for SQLite databases
//    		return generateStatementsForSQLiteDatabase(database);
//    	}

    	return new SqlStatement[] { new SetNullableStatement(
    			getSchemaName() == null?database.getDefaultSchemaName():getSchemaName(), 
    			getTableName(), getColumnName(), getColumnDataType(), true) 
    	};
    }
    
    private SqlStatement[] generateStatementsForSQLiteDatabase(Database database) {
    	// SQLite does not support this ALTER TABLE operation until now.
		// For more information see: http://www.sqlite.org/omitted.html.
		// This is a small work around...
		
    	List<SqlStatement> statements = new ArrayList<SqlStatement>();
    	
		// define alter table logic
		AlterTableVisitor rename_alter_visitor = new AlterTableVisitor() {
			public ColumnConfig[] getColumnsToAdd() {
				return new ColumnConfig[0];
			}
			public boolean copyThisColumn(ColumnConfig column) {
				return true;
			}
			public boolean createThisColumn(ColumnConfig column) {
				if (column.getName().equals(getColumnName())) {
					column.getConstraints().setNullable(true);
				}
				return true;
			}
			public boolean createThisIndex(Index index) {
				return true;
			}
		};
    		
    	try {
    		// alter table
			statements.addAll(SQLiteDatabase.getAlterTableStatements(
					rename_alter_visitor,
					database,getSchemaName(),getTableName()));
		} catch (Exception e) {
			e.printStackTrace();
		}
		return statements.toArray(new SqlStatement[statements.size()]);		
    }

    @Override
    protected Change[] createInverses() {
        AddNotNullConstraintChange inverse = new AddNotNullConstraintChange();
        inverse.setColumnName(getColumnName());
        inverse.setSchemaName(getSchemaName());
        inverse.setTableName(getTableName());
        inverse.setColumnDataType(getColumnDataType());

        return new Change[]{
                inverse
        };
    }

    public String getConfirmationMessage() {
        return "Null constraint dropped from " + getTableName() + "." + getColumnName();
    }
}