!115 feat: 新增 IF、IFNULL 函数

Merge pull request !115 from 王帅/main

mybatis-flex-core/src/main/java/com/mybatisflex/core/query/IfFunctionQueryColumn.java

@@ -0,0 +1,74 @@
+/*
+ *  Copyright (c) 2022-2023, Mybatis-Flex (fuhai999@gmail.com).
+ *  <p>
+ *  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
+ *  <p>
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *  <p>
+ *  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 com.mybatisflex.core.query;
+
+import com.mybatisflex.core.dialect.IDialect;
+import com.mybatisflex.core.util.ArrayUtil;
+
+import java.util.List;
+
+/**
+ * IF 函数查询列。
+ *
+ * @author 王帅
+ * @since 2023-07-07
+ */
+public class IfFunctionQueryColumn extends QueryColumn implements HasParamsColumn {
+
+    private QueryCondition condition;
+    private QueryColumn trueValue;
+    private QueryColumn falseValue;
+
+    public IfFunctionQueryColumn(QueryCondition condition, QueryColumn trueValue, QueryColumn falseValue) {
+        this.condition = condition;
+        this.trueValue = trueValue;
+        this.falseValue = falseValue;
+    }
+
+    @Override
+    String toConditionSql(List<QueryTable> queryTables, IDialect dialect) {
+        return "IF(" + condition.toSql(queryTables, dialect) + ", " +
+                trueValue.toConditionSql(queryTables, dialect) + ", " +
+                falseValue.toConditionSql(queryTables, dialect) + ")";
+    }
+
+    @Override
+    public Object[] getParamValues() {
+        Object[] params = WrapperUtil.getValues(condition);
+        // IF 函数嵌套
+        if (trueValue instanceof HasParamsColumn) {
+            Object[] paramValues = ((HasParamsColumn) trueValue).getParamValues();
+            params = ArrayUtil.concat(params, paramValues);
+        }
+        if (falseValue instanceof HasParamsColumn) {
+            Object[] paramValues = ((HasParamsColumn) falseValue).getParamValues();
+            params = ArrayUtil.concat(params, paramValues);
+        }
+        return params;
+    }
+
+    @Override
+    public IfFunctionQueryColumn clone() {
+        IfFunctionQueryColumn clone = (IfFunctionQueryColumn) super.clone();
+        // deep clone ...
+        clone.condition = this.condition.clone();
+        clone.trueValue = this.trueValue.clone();
+        clone.falseValue = this.falseValue.clone();
+        return clone;
+    }
+
+}

mybatis-flex-core/src/main/java/com/mybatisflex/core/query/QueryMethods.java

@@ -2387,6 +2387,13 @@ public class QueryMethods {
 
     // === 构建 column 列 ===
 
+    /**
+     * 构建 NULL 常量。
+     */
+    public static QueryColumn null_() {
+        return new StringQueryColumn("NULL");
+    }
+
     /**
      * 构建数字常量。
      */
@@ -2436,6 +2443,50 @@ public class QueryMethods {
         return new SelectQueryColumn(queryWrapper);
     }
 
+    // === IF 函数 ===
+
+    /**
+     * IF 函数。
+     */
+    public static QueryColumn if_(QueryCondition condition, String trueColumn, String falseColumn) {
+        return new IfFunctionQueryColumn(condition, new QueryColumn(trueColumn), new QueryColumn(falseColumn));
+    }
+
+    /**
+     * IF 函数。
+     */
+    public static QueryColumn if_(QueryCondition condition, QueryColumn trueColumn, QueryColumn falseColumn) {
+        return new IfFunctionQueryColumn(condition, trueColumn, falseColumn);
+    }
+
+    /**
+     * IF 函数。
+     */
+    public static <T, F> QueryColumn if_(QueryCondition condition, LambdaGetter<T> trueColumn, LambdaGetter<F> falseColumn) {
+        return new IfFunctionQueryColumn(condition, LambdaUtil.getQueryColumn(trueColumn), LambdaUtil.getQueryColumn(falseColumn));
+    }
+
+    /**
+     * IFNULL 函数。
+     */
+    public static QueryColumn ifNull(String nullColumn, String elseColumn) {
+        return new FunctionQueryColumn("IFNULL", new QueryColumn(nullColumn), new QueryColumn(elseColumn));
+    }
+
+    /**
+     * IFNULL 函数。
+     */
+    public static QueryColumn ifNull(QueryColumn nullColumn, QueryColumn elseColumn) {
+        return new FunctionQueryColumn("IFNULL", nullColumn, elseColumn);
+    }
+
+    /**
+     * IFNULL 函数。
+     */
+    public static <N, E> QueryColumn ifNull(LambdaGetter<N> nullColumn, LambdaGetter<E> elseColumn) {
+        return new FunctionQueryColumn("IFNULL", LambdaUtil.getQueryColumn(nullColumn), LambdaUtil.getQueryColumn(elseColumn));
+    }
+
     // === 构建 QueryCondition 查询条件 ===
 
     /**

mybatis-flex-core/src/test/java/com/mybatisflex/coretest/IfFunctionTest.java

@@ -0,0 +1,67 @@
+/*
+ *  Copyright (c) 2022-2023, Mybatis-Flex (fuhai999@gmail.com).
+ *  <p>
+ *  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
+ *  <p>
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *  <p>
+ *  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 com.mybatisflex.coretest;
+
+import com.mybatisflex.core.query.QueryWrapper;
+import org.junit.Test;
+
+import static com.mybatisflex.core.query.QueryMethods.*;
+import static com.mybatisflex.coretest.table.AccountTableDef.ACCOUNT;
+
+/**
+ * @author 王帅
+ * @since 2023-07-07
+ */
+public class IfFunctionTest {
+
+    @Test
+    public void test01() {
+        QueryWrapper queryWrapper = QueryWrapper.create()
+                .select(if_(ACCOUNT.AGE.ge(6), ACCOUNT.IS_NORMAL, ACCOUNT.IS_DELETE).as("type"))
+                .from(ACCOUNT)
+                .where(ACCOUNT.ID.eq(1));
+        System.out.println(queryWrapper.toSQL());
+    }
+
+    @Test
+    public void test02() {
+        QueryWrapper queryWrapper = QueryWrapper.create()
+                .select(if_(ACCOUNT.AGE.ge(18), string("成年人"),
+                        if_(ACCOUNT.AGE.le(8), string("未上学"), string("已上学"))).as("type"))
+                .from(ACCOUNT)
+                .where(ACCOUNT.ID.eq(1));
+        System.out.println(queryWrapper.toSQL());
+    }
+
+    @Test
+    public void test03() {
+        QueryWrapper queryWrapper = QueryWrapper.create()
+                .select(ifNull(ACCOUNT.ID, number(0)))
+                .from(ACCOUNT)
+                .where(ACCOUNT.ID.eq(1));
+        System.out.println(queryWrapper.toSQL());
+    }
+
+    @Test
+    public void test04() {
+        QueryWrapper queryWrapper = QueryWrapper.create()
+                .select(ifNull(null_(), number(0)))
+                .from(ACCOUNT);
+        System.out.println(queryWrapper.toSQL());
+    }
+
+}