Better pattern for decorating a select statement

Author: jeffgbutler

src/main/java/org/mybatis/dynamic/sql/util/mybatis3/MyBatis3Utils.java

@@ -39,7 +39,6 @@
 import org.mybatis.dynamic.sql.select.CountDSLCompleter;
 import org.mybatis.dynamic.sql.select.QueryExpressionDSL;
 import org.mybatis.dynamic.sql.select.SelectDSLCompleter;
-import org.mybatis.dynamic.sql.select.SelectModel;
 import org.mybatis.dynamic.sql.select.render.SelectStatementProvider;
 import org.mybatis.dynamic.sql.update.UpdateDSLCompleter;
 import org.mybatis.dynamic.sql.update.render.UpdateStatementProvider;

src/test/java/examples/paging/LimitAndOffsetAdapter.java

@@ -0,0 +1,47 @@
+/*
+ *    Copyright 2016-2025 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 examples.paging;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.jspecify.annotations.NullMarked;
+import org.mybatis.dynamic.sql.select.render.SelectStatementProvider;
+
+@NullMarked
+public class LimitAndOffsetDecorator implements SelectStatementProvider {
+    private final Map<String, Object> parameters = new HashMap<>();
+    private final String selectStatement;
+
+    public LimitAndOffsetDecorator(int limit, int offset, SelectStatementProvider delegate) {
+        parameters.putAll(delegate.getParameters());
+        parameters.put("limit", limit);
+        parameters.put("offset", offset);
+
+        selectStatement = delegate.getSelectStatement() +
+                " LIMIT #{parameters.limit} OFFSET #{parameters.offset}";
+    }
+
+    @Override
+    public Map<String, Object> getParameters() {
+        return parameters;
+    }
+
+    @Override
+    public String getSelectStatement() {
+        return selectStatement;
+    }
+}

src/test/java/examples/paging/LimitAndOffsetDecorator.java

@@ -15,11 +15,15 @@
  */
 package examples.paging;
 
+import static examples.animal.data.AnimalDataDynamicSqlSupport.*;
+
 import java.util.List;
 
 import org.apache.ibatis.annotations.Result;
-import org.apache.ibatis.annotations.Results;
 import org.apache.ibatis.annotations.SelectProvider;
+import org.mybatis.dynamic.sql.render.RenderingStrategies;
+import org.mybatis.dynamic.sql.select.SelectDSL;
+import org.mybatis.dynamic.sql.select.SelectDSLCompleter;
 import org.mybatis.dynamic.sql.select.render.SelectStatementProvider;
 import org.mybatis.dynamic.sql.util.SqlProviderAdapter;
 
@@ -28,11 +32,16 @@
 public interface LimitAndOffsetMapper {
 
     @SelectProvider(type=SqlProviderAdapter.class, method="select")
-    @Results(id="AnimalDataResult", value={
-        @Result(column="id", property="id", id=true),
-        @Result(column="animal_name", property="animalName"),
-        @Result(column="brain_weight", property="brainWeight"),
-        @Result(column="body_weight", property="bodyWeight")
-    })
+    @Result(column="id", property="id", id=true)
+    @Result(column="animal_name", property="animalName")
+    @Result(column="brain_weight", property="brainWeight")
+    @Result(column="body_weight", property="bodyWeight")
     List<AnimalData> selectMany(SelectStatementProvider selectStatement);
+
+    default List<AnimalData> selectWithLimitAndOffset(int limit, int offset, SelectDSLCompleter completer) {
+        var dslStart = SelectDSL.select(id, animalName, brainWeight, bodyWeight).from(animalData);
+        var selectStatement = completer.apply(dslStart).build().render(RenderingStrategies.MYBATIS3);
+        var decorator = new LimitAndOffsetDecorator(limit, offset, selectStatement);
+        return selectMany(decorator);
+    }
 }

src/test/java/examples/paging/LimitAndOffsetMapper.java

@@ -25,6 +25,7 @@
 import java.sql.DriverManager;
 import java.util.List;
 
+import examples.animal.data.AnimalData;
 import org.apache.ibatis.datasource.unpooled.UnpooledDataSource;
 import org.apache.ibatis.jdbc.ScriptRunner;
 import org.apache.ibatis.mapping.Environment;
@@ -35,10 +36,8 @@
 import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-
-import examples.animal.data.AnimalData;
 import org.mybatis.dynamic.sql.SqlBuilder;
-import org.mybatis.dynamic.sql.select.SelectModel;
+import org.mybatis.dynamic.sql.render.RenderingStrategies;
 import org.mybatis.dynamic.sql.select.render.SelectStatementProvider;
 
 class LimitAndOffsetTest {
@@ -71,14 +70,27 @@ void testLimitAndOffset() {
         try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
             LimitAndOffsetMapper mapper = sqlSession.getMapper(LimitAndOffsetMapper.class);
 
-            SelectModel selectModel = SqlBuilder.select(id, animalName, brainWeight, bodyWeight)
+            List<AnimalData> rows = mapper.selectWithLimitAndOffset(5, 3, d -> d.orderBy(id));
+
+            assertThat(rows).hasSize(5);
+            assertThat(rows.get(0).getId()).isEqualTo(4);
+        }
+    }
+
+    @Test
+    void testLimitAndOffsetDirect() {
+        try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+            LimitAndOffsetMapper mapper = sqlSession.getMapper(LimitAndOffsetMapper.class);
+
+            SelectStatementProvider selectStatement = SqlBuilder.select(id, animalName, brainWeight, bodyWeight)
                     .from(animalData)
                     .orderBy(id)
-                    .build();
+                    .build()
+                    .render(RenderingStrategies.MYBATIS3);
 
-            SelectStatementProvider selectStatement = new LimitAndOffsetAdapter(5, 3).apply(selectModel);
+            SelectStatementProvider decorator = new LimitAndOffsetDecorator(5, 3, selectStatement);
 
-            List<AnimalData> rows = mapper.selectMany(selectStatement);
+            List<AnimalData> rows = mapper.selectMany(decorator);
 
             assertThat(rows).hasSize(5);
             assertThat(rows.get(0).getId()).isEqualTo(4);