Merge pull request #219 from jeffgbutler/gh_197

Add support for functions that change column data types

Author: jeffgbutler

CHANGELOG.md

@@ -10,6 +10,7 @@ GitHub milestone: [https://github.com/mybatis/mybatis-dynamic-sql/issues?q=miles
 
 - Added a general insert statement that does not require a separate record class to hold values for the insert. ([#201](https://github.com/mybatis/mybatis-dynamic-sql/issues/201))
 - Added the capability to specify a rendering strategy on a column to override the defaut rendering strategy for a statement. This will allow certain edge cases where a parameter marker needs to be formatted in a unique way (for example, "::jsonb" needs to be added to parameter markers for JSON fields in PostgreSQL) ([#200](https://github.com/mybatis/mybatis-dynamic-sql/issues/200))
+- Added the ability to write a function that will change the column data type ([#197](https://github.com/mybatis/mybatis-dynamic-sql/issues/197))
 
 ## Release 1.1.4 - November 23, 2019
 

src/main/java/org/mybatis/dynamic/sql/select/function/AbstractFunction.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2016-2018 the original author or authors.
+ *    Copyright 2016-2020 the original author or authors.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -16,31 +16,17 @@
 package org.mybatis.dynamic.sql.select.function;
 
 import java.sql.JDBCType;
-import java.util.Objects;
 import java.util.Optional;
 
 import org.mybatis.dynamic.sql.BindableColumn;
 
-public abstract class AbstractFunction<T, U extends AbstractFunction<T, U>> implements BindableColumn<T> {
-    protected BindableColumn<T> column;
-    protected String alias;
+public abstract class AbstractFunction<T, U extends AbstractFunction<T, U>>
+        extends AbstractTypeConvertingFunction<T, T, U> {
 
     protected AbstractFunction(BindableColumn<T> column) {
-        this.column = Objects.requireNonNull(column);
+        super(column);
     }
 
-    @Override
-    public Optional<String> alias() {
-        return Optional.ofNullable(alias);
-    }
-
-    @Override
-    public U as(String alias) {
-        U newThing = copy();
-        newThing.alias = alias;
-        return newThing;
-    }
-
     @Override
     public Optional<JDBCType> jdbcType() {
         return column.jdbcType();
@@ -50,6 +36,4 @@ public Optional<JDBCType> jdbcType() {
     public Optional<String> typeHandler() {
         return column.typeHandler();
     }
-    
-    protected abstract U copy();
 }

src/main/java/org/mybatis/dynamic/sql/select/function/AbstractTypeConvertingFunction.java

@@ -0,0 +1,59 @@
+/**
+ *    Copyright 2016-2020 the original author or authors.
+ *
+ *    Licensed 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.mybatis.dynamic.sql.select.function;
+
+import java.util.Objects;
+import java.util.Optional;
+
+import org.mybatis.dynamic.sql.BindableColumn;
+
+/**
+ * Represents a function that can change the underlying type. For example, converting a binary field for a base64
+ * string, or an integer to a string, etc.
+ * 
+ * <p>Thanks to @endink for the idea.
+ * 
+ * @author Jeff Butler
+ *
+ * @param <T> The type of the underlying column. For example, if a function converts a VARCHR to an INT, then the
+ *     underlying type will be a String 
+ * @param <R> The type of the column after the conversion. For example, if a function converts a VARCHR to an INT, then
+ *     the converted type will be Integer
+ * @param <U> the specific subtype that implements the function
+ */
+public abstract class AbstractTypeConvertingFunction<T, R, U extends AbstractTypeConvertingFunction<T, R, U>>
+        implements BindableColumn<R> {
+    protected BindableColumn<T> column;
+    protected String alias;
+
+    protected AbstractTypeConvertingFunction(BindableColumn<T> column) {
+        this.column = Objects.requireNonNull(column);
+    }
+    
+    @Override
+    public Optional<String> alias() {
+        return Optional.ofNullable(alias);
+    }
+
+    @Override
+    public U as(String alias) {
+        U newThing = copy();
+        newThing.alias = alias;
+        return newThing;
+    }
+
+    protected abstract U copy();
+}

src/test/java/examples/type_conversion/MyFilesDynamicSqlSupport.java

@@ -0,0 +1,36 @@
+/**
+ *    Copyright 2016-2020 the original author or authors.
+ *
+ *    Licensed 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 examples.type_conversion;
+
+import java.sql.JDBCType;
+
+import org.mybatis.dynamic.sql.SqlColumn;
+import org.mybatis.dynamic.sql.SqlTable;
+
+public final class MyFilesDynamicSqlSupport {
+    public static final MyFiles myfiles = new MyFiles();
+    public static final SqlColumn<Integer> fileId = myfiles.fileId;
+    public static final SqlColumn<byte[]> fileContents = myfiles.fileContents;
+
+    public static final class MyFiles extends SqlTable {
+        public final SqlColumn<Integer> fileId = column("file_id", JDBCType.INTEGER);
+        public final SqlColumn<byte[]> fileContents = column("file_contents", JDBCType.LONGVARBINARY);
+
+        public MyFiles() {
+            super("MyFiles");
+        }
+    }
+}

src/test/java/examples/type_conversion/MyFilesMapper.java

@@ -0,0 +1,33 @@
+/**
+ *    Copyright 2016-2020 the original author or authors.
+ *
+ *    Licensed 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 examples.type_conversion;
+
+import java.util.Map;
+
+import org.apache.ibatis.annotations.InsertProvider;
+import org.apache.ibatis.annotations.SelectProvider;
+import org.mybatis.dynamic.sql.insert.render.GeneralInsertStatementProvider;
+import org.mybatis.dynamic.sql.select.render.SelectStatementProvider;
+import org.mybatis.dynamic.sql.util.SqlProviderAdapter;
+
+public interface MyFilesMapper {
+
+    @InsertProvider(type=SqlProviderAdapter.class, method="generalInsert")
+    int insert(GeneralInsertStatementProvider insertStatement);
+    
+    @SelectProvider(type=SqlProviderAdapter.class, method="select")
+    Map<String, Object> generalSelect(SelectStatementProvider selectStatement);
+}

src/test/java/examples/type_conversion/ToBase64.java

@@ -0,0 +1,56 @@
+/**
+ *    Copyright 2016-2020 the original author or authors.
+ *
+ *    Licensed 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 examples.type_conversion;
+
+import java.sql.JDBCType;
+import java.util.Optional;
+
+import org.mybatis.dynamic.sql.BindableColumn;
+import org.mybatis.dynamic.sql.render.TableAliasCalculator;
+import org.mybatis.dynamic.sql.select.function.AbstractTypeConvertingFunction;
+
+public class ToBase64 extends AbstractTypeConvertingFunction<byte[], String, ToBase64> {
+
+    protected ToBase64(BindableColumn<byte[]> column) {
+        super(column);
+    }
+
+    @Override
+    public Optional<JDBCType> jdbcType() {
+        return Optional.of(JDBCType.VARCHAR);
+    }
+
+    @Override
+    public Optional<String> typeHandler() {
+        return Optional.empty();
+    }
+
+    @Override
+    public String renderWithTableAlias(TableAliasCalculator tableAliasCalculator) {
+        return "TO_BASE64(" //$NON-NLS-1$
+                + column.renderWithTableAlias(tableAliasCalculator)
+                + ")"; //$NON-NLS-1$
+    }
+
+    @Override
+    protected ToBase64 copy() {
+        return new ToBase64(column);
+    }
+    
+    public static ToBase64 toBase64(BindableColumn<byte[]> column) {
+        return new ToBase64(column);
+    }
+}