METAMODEL-1225 Add ColumnTypingStrategies and use them in CSV module.

core/src/main/java/org/apache/metamodel/schema/typing/ColumnTypingContext.java

@@ -0,0 +1,52 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.metamodel.schema.typing;
+
+import org.apache.metamodel.schema.ColumnType;
+import org.apache.metamodel.schema.Table;
+
+/**
+ * Defines the context for configuring the type for a single column in a
+ * {@link ColumnTypingStrategy} session.
+ */
+public interface ColumnTypingContext {
+
+    /**
+     * Gets the index of the column being configured.
+     *
+     * @return the column index
+     */
+    int getColumnIndex();
+
+    /**
+     * Gets the {@link Table} that the column is to pertain to. If the table is
+     * not yet available then this may return null.
+     *
+     * @return the associated table
+     */
+    Table getTable();
+
+    /**
+     * Gets the intrinsic column type, if this is defined in the datastore
+     * itself. This may be in the form of a header or such.
+     *
+     * @return the column type representing the datastore's column type
+     */
+    ColumnType getIntrinsicColumnType();
+}

core/src/main/java/org/apache/metamodel/schema/typing/ColumnTypingContextImpl.java

@@ -0,0 +1,76 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.metamodel.schema.typing;
+
+import org.apache.metamodel.schema.ColumnType;
+import org.apache.metamodel.schema.Table;
+
+
+/**
+ * An implementation of {@link ColumnTypingContext} that holds necessary context about the column being configured.
+ */
+public class ColumnTypingContextImpl implements ColumnTypingContext {
+
+    private final int columnIndex;
+
+    private final Table table;
+
+    private final ColumnType intrinsicColumnType;
+
+
+    /**
+     * Creates a context to conifgure a column for a specific table.
+     * @param table               The table that contains the column
+     * @param intrinsicColumnType The column type that represents the type configured in the datastore
+     * @param columnIndex         the index in the table of the column being configured.
+     */
+    public ColumnTypingContextImpl( Table table, ColumnType intrinsicColumnType, int columnIndex ) {
+        this.table = table;
+        this.intrinsicColumnType = intrinsicColumnType;
+        this.columnIndex = columnIndex;
+    }
+
+
+    /**
+     * Creates a context a column to be configured.
+     * @param columnIndex the index in the table of the column being configured.
+     */
+    public ColumnTypingContextImpl( int columnIndex ) {
+        this( null, null, columnIndex );
+    }
+
+
+    @Override
+    public int getColumnIndex() {
+        return columnIndex;
+    }
+
+
+    @Override
+    public Table getTable() {
+        return table;
+    }
+
+
+    @Override
+    public ColumnType getIntrinsicColumnType() {
+        return intrinsicColumnType;
+    }
+
+}

core/src/main/java/org/apache/metamodel/schema/typing/ColumnTypingSession.java

@@ -0,0 +1,48 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.metamodel.schema.typing;
+
+
+import org.apache.metamodel.schema.Column;
+import org.apache.metamodel.schema.ColumnType;
+import org.apache.metamodel.schema.Table;
+
+import java.io.Closeable;
+
+/**
+ * Represents a 'session' in which a single {@link Table}'s {@link Column}s are
+ * assigned {@link ColumnType}s.
+ */
+public interface ColumnTypingSession extends Closeable {
+
+    /**
+     * Provides the type to apply for a given column.
+     *
+     * @param ctx the context of the column naming taking place. This contains
+     *            column index, intrinsic type etc. if available.
+     * @return the type to provide to the column.
+     */
+    public ColumnType getNextColumnType( ColumnTypingContext ctx );
+
+    /**
+     * Ends the column typing session.
+     */
+    @Override
+    void close();
+}

core/src/main/java/org/apache/metamodel/schema/typing/ColumnTypingStrategies.java

@@ -0,0 +1,67 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.metamodel.schema.typing;
+
+import org.apache.metamodel.schema.ColumnType;
+
+import java.util.List;
+
+/**
+ * Constructors and common utilities for {@link ColumnTypingStrategy} objects.
+ */
+public class ColumnTypingStrategies {
+
+    private static final DefaultColumnTypingStrategy DEFAULT_STRATEGY = new DefaultColumnTypingStrategy();
+
+
+    private ColumnTypingStrategies() {
+    }
+
+
+    /**
+     * The default strategy assumes all column types are text.
+     *
+     * @return a strategy that defaults to text
+     */
+    public static ColumnTypingStrategy defaultStrategy() {
+        return DEFAULT_STRATEGY;
+    }
+
+
+    /**
+     * Utility to create a {@link CustomColumnTypingStrategy}.
+     *
+     * @param columnTypes the types of each column
+     * @return a strategy for custom type configuration
+     */
+    public static ColumnTypingStrategy customTypes( List<ColumnType> columnTypes ) {
+        return new CustomColumnTypingStrategy( columnTypes );
+    }
+
+
+    /**
+     * Utility to create a {@link CustomColumnTypingStrategy}.
+     *
+     * @param columnTypes the types of each column
+     * @return a strategy for custom type configuration
+     */
+    public static ColumnTypingStrategy customTypes( ColumnType... columnTypes ) {
+        return new CustomColumnTypingStrategy( columnTypes );
+    }
+}

core/src/main/java/org/apache/metamodel/schema/typing/ColumnTypingStrategy.java

@@ -0,0 +1,33 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.metamodel.schema.typing;
+
+
+import java.io.Serializable;
+
+/**
+ * A strategy that defines the data types of columns. Such strategies are
+ * mostly used when a particular datastore is not itself intrinsically
+ * specifying the column type.
+ */
+public interface ColumnTypingStrategy extends Serializable {
+
+    ColumnTypingSession startColumnTypingSession();
+
+}

core/src/main/java/org/apache/metamodel/schema/typing/CustomColumnTypingStrategy.java

@@ -0,0 +1,76 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.metamodel.schema.typing;
+
+import org.apache.metamodel.schema.ColumnType;
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ * A {@link ColumnTypingStrategy} that allows the user to supply his own list of column types
+ */
+public class CustomColumnTypingStrategy implements ColumnTypingStrategy {
+
+    private static final long serialVersionUID = 1L;
+
+    private final List<ColumnType> columnTypes;
+
+
+    /**
+     * Creates the strategy based on the provided types.
+     *
+     * @param columnTypes a list of column types to be applied to a table.
+     */
+    public CustomColumnTypingStrategy( List<ColumnType> columnTypes ) {
+        this.columnTypes = columnTypes;
+    }
+
+
+    /**
+     * Creates the strategy based on the provided types.
+     *
+     * @param columnTypes a list of column types to be applied to a table.
+     */
+    public CustomColumnTypingStrategy( ColumnType... columnTypes ) {
+        this( Arrays.asList( columnTypes ) );
+    }
+
+
+    @Override
+    public ColumnTypingSession startColumnTypingSession() {
+        final Iterator<ColumnType> iterator = columnTypes.iterator();
+        return new ColumnTypingSession() {
+
+            @Override
+            public ColumnType getNextColumnType( ColumnTypingContext ctx ) {
+                if ( iterator.hasNext() ) {
+                    return iterator.next();
+                }
+                return null;
+            }
+
+
+            @Override
+            public void close() {
+            }
+        };
+    }
+}