Support the _databaseId variable in sql template

src/main/java/org/mybatis/scripting/freemarker/FreeMarkerSqlSource.java

@@ -21,6 +21,7 @@
 import java.util.HashMap;
 import java.util.Map;
 
+import freemarker.template.SimpleScalar;
 import org.apache.ibatis.builder.SqlSourceBuilder;
 import org.apache.ibatis.mapping.BoundSql;
 import org.apache.ibatis.mapping.SqlSource;
@@ -40,13 +41,15 @@ public class FreeMarkerSqlSource implements SqlSource {
   private final Template template;
   private final Configuration configuration;
   private final Version incompatibleImprovementsVersion;
+  private final String databaseId;
 
   public static final String GENERATED_PARAMS_KEY = "__GENERATED__";
 
   public FreeMarkerSqlSource(Template template, Configuration configuration, Version incompatibleImprovementsVersion) {
     this.template = template;
     this.configuration = configuration;
     this.incompatibleImprovementsVersion = incompatibleImprovementsVersion;
+    this.databaseId = configuration.getDatabaseId();
   }
 
   /**
@@ -56,9 +59,12 @@ public FreeMarkerSqlSource(Template template, Configuration configuration, Versi
   protected Object preProcessDataContext(Object dataContext, boolean isMap) {
     if (isMap) {
       ((Map<String, Object>) dataContext).put(MyBatisParamDirective.DEFAULT_KEY, new MyBatisParamDirective());
+      ((Map<String, Object>) dataContext).put(MyBatisParamDirective.DATABASE_ID_KEY,new SimpleScalar(this.databaseId));
     } else {
       ((ParamObjectAdapter) dataContext).putAdditionalParam(MyBatisParamDirective.DEFAULT_KEY,
           new MyBatisParamDirective());
+      ((ParamObjectAdapter) dataContext).putAdditionalParam(MyBatisParamDirective.DATABASE_ID_KEY,
+              new SimpleScalar(this.databaseId));
     }
     return dataContext;
   }

src/main/java/org/mybatis/scripting/freemarker/MyBatisParamDirective.java

@@ -76,6 +76,7 @@
  */
 public class MyBatisParamDirective implements TemplateDirectiveModel {
   public static String DEFAULT_KEY = "p";
+  public static String DATABASE_ID_KEY = "_databaseId";
 
   @Override
   public void execute(Environment env, Map params, TemplateModel[] loopVars, TemplateDirectiveBody body)

src/test/java/org/mybatis/scripting/freemarker/PreparedDatabaseIdParamsMapper.java

@@ -0,0 +1,29 @@
+/*
+ *    Copyright 2015-2023 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
+ *
+ *       https://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.scripting.freemarker;
+
+import org.apache.ibatis.annotations.Lang;
+import org.apache.ibatis.annotations.Param;
+import org.apache.ibatis.annotations.Select;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface PreparedDatabaseIdParamsMapper {
+  @Lang(FreeMarkerLanguageDriver.class)
+  @Select("preparedDatabaseIdTest.ftl")
+  Optional<Name> getDatabaseIdTest();
+}

src/test/java/org/mybatis/scripting/freemarker/PreparedDatabaseIdParamsTest.java

@@ -0,0 +1,93 @@
+/*
+ *    Copyright 2015-2023 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
+ *
+ *       https://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.scripting.freemarker;
+
+import java.io.Reader;
+import java.sql.Connection;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.ibatis.exceptions.PersistenceException;
+import org.apache.ibatis.io.Resources;
+import org.apache.ibatis.jdbc.ScriptRunner;
+import org.apache.ibatis.mapping.Environment;
+import org.apache.ibatis.session.Configuration;
+import org.apache.ibatis.session.SqlSession;
+import org.apache.ibatis.session.SqlSessionFactory;
+import org.apache.ibatis.session.SqlSessionFactoryBuilder;
+import org.apache.ibatis.transaction.TransactionFactory;
+import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory;
+import org.hsqldb.jdbc.JDBCDataSource;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import java.util.Optional;
+
+/**
+ * Test of using FreeMarker to generate prepared statements parameters.
+ *
+ * @author s-nakao
+ */
+class PreparedDatabaseIdParamsTest {
+  private static SqlSessionFactory sqlSessionFactory;
+
+  @BeforeAll
+  static void setUp() throws Exception {
+    Class.forName("org.hsqldb.jdbcDriver");
+
+    JDBCDataSource dataSource = new JDBCDataSource();
+    dataSource.setUrl("jdbc:hsqldb:mem:db5");
+    dataSource.setUser("sa");
+    dataSource.setPassword("");
+
+    try (Connection conn = dataSource.getConnection()) {
+      try (Reader reader = Resources.getResourceAsReader("org/mybatis/scripting/freemarker/create-db.sql")) {
+        ScriptRunner runner = new ScriptRunner(conn);
+        runner.setLogWriter(null);
+        runner.setErrorLogWriter(null);
+        runner.runScript(reader);
+        conn.commit();
+      }
+    }
+
+    TransactionFactory transactionFactory = new JdbcTransactionFactory();
+    Environment environment = new Environment("development", transactionFactory, dataSource);
+
+    // You can call configuration.setDefaultScriptingLanguage(FreeMarkerLanguageDriver.class)
+    // after this to use FreeMarker driver by default.
+    Configuration configuration = new Configuration(environment);
+
+    // set databaseId. default null
+    // If it is a property, please refer to the following
+    // https://mybatis.org/mybatis-3/ja/configuration.html#databaseIdProvider.
+    configuration.setDatabaseId("hsqldb");
+
+    configuration.addMapper(PreparedDatabaseIdParamsMapper.class);
+    sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);
+  }
+
+  @Test
+  void testInCall() {
+    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+      PreparedDatabaseIdParamsMapper mapper = sqlSession.getMapper(PreparedDatabaseIdParamsMapper.class);
+      Optional<Name> nameList = mapper.getDatabaseIdTest();
+      Assertions.assertEquals(true, nameList.isPresent());
+      Assertions.assertEquals("Fred", nameList.get().getFirstName());
+      Assertions.assertEquals("Flintstone", nameList.get().getLastName());
+    }
+  }
+}

src/test/resources/sql/preparedDatabaseIdTest.ftl

@@ -0,0 +1,23 @@
+<#--
+
+       Copyright 2015-2023 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
+
+          https://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.
+
+-->
+select
+    *
+from
+    names
+where
+    <#if '${_databaseId}' == 'hsqldb'>firstName = 'Fred' and lastName = 'Flintstone'</#if>