feat: add sql case grammar support

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

@@ -0,0 +1,135 @@
+/**
+ * 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 com.mybatisflex.core.util.LambdaGetter;
+import com.mybatisflex.core.util.LambdaUtil;
+import com.mybatisflex.core.util.StringUtil;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class CaseQueryColumn extends QueryColumn implements HasParamsColumn{
+
+    private List<When> whens;
+    private Object elseValue;
+
+    void addWhen(When when) {
+        if (whens == null) {
+            whens = new ArrayList<>();
+        }
+        whens.add(when);
+    }
+
+
+    @Override
+    String toSelectSql(List<QueryTable> queryTables, IDialect dialect) {
+        StringBuilder sql = new StringBuilder("CASE");
+        for (When when : whens) {
+            sql.append(" WHEN ").append(when.whenCondition.toSql(queryTables, dialect));
+            sql.append(" THEN ").append(buildValue(when.thenValue));
+        }
+        if (elseValue != null) {
+            sql.append(" ELSE ").append(buildValue(elseValue));
+        }
+        sql.append(" END");
+        if (StringUtil.isNotBlank(alias)) {
+            return "(" + sql + ") AS " + dialect.wrap(alias);
+        }
+        return sql.toString();
+    }
+
+
+    @Override
+    String toConditionSql(List<QueryTable> queryTables, IDialect dialect) {
+        StringBuilder sql = new StringBuilder("CASE");
+        for (When when : whens) {
+            sql.append(" WHEN ").append(when.whenCondition.toSql(queryTables, dialect));
+            sql.append(" THEN ").append(buildValue(when.thenValue));
+        }
+        if (elseValue != null) {
+            sql.append(" ELSE ").append(buildValue(elseValue));
+        }
+        sql.append(" END");
+        return "(" + sql + ")";
+    }
+
+    @Override
+    public QueryColumn as(String alias) {
+        this.alias = alias;
+        return this;
+    }
+
+    @Override
+    public <T> QueryColumn as(LambdaGetter<T> fn) {
+        return as(LambdaUtil.getFieldName(fn));
+    }
+
+    private String buildValue(Object value) {
+        if (value instanceof Number || value instanceof Boolean) {
+            return String.valueOf(value);
+        } else {
+            return "'" + value + "'";
+        }
+    }
+
+    @Override
+    public Object[] getParamValues() {
+        Object[] values = new Object[0];
+        for (When when : whens) {
+            values = ArrayUtil.concat(values, WrapperUtil.getValues(when.whenCondition));
+        }
+        return values;
+    }
+
+
+    public static class When {
+        private Builder builder;
+        private QueryCondition whenCondition;
+        private Object thenValue;
+
+        public When(Builder builder, QueryCondition whenCondition) {
+            this.builder = builder;
+            this.whenCondition = whenCondition;
+        }
+
+        public Builder then(Object thenValue) {
+            this.thenValue = thenValue;
+            this.builder.caseQueryColumn.addWhen(this);
+            return builder;
+        }
+    }
+
+    public static class Builder {
+
+        private CaseQueryColumn caseQueryColumn = new CaseQueryColumn();
+
+        public When when(QueryCondition condition) {
+            return new When(this, condition);
+        }
+
+        public Builder else_(Object elseValue) {
+            caseQueryColumn.elseValue = elseValue;
+            return this;
+        }
+
+        public CaseQueryColumn end() {
+            return caseQueryColumn;
+        }
+    }
+}

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

@@ -0,0 +1,130 @@
+/**
+ * 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.LambdaGetter;
+import com.mybatisflex.core.util.LambdaUtil;
+import com.mybatisflex.core.util.StringUtil;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class CaseSearchQueryColumn extends QueryColumn {
+
+    private QueryColumn queryColumn;
+    private List<When> whens;
+    private Object elseValue;
+
+    @Override
+    String toSelectSql(List<QueryTable> queryTables, IDialect dialect) {
+        StringBuilder sql = new StringBuilder("CASE ");
+        sql.append(queryColumn.toSelectSql(queryTables, dialect));
+        for (When when : whens) {
+            sql.append(" WHEN ").append(buildValue(when.searchValue)).append(" THEN ").append(buildValue(when.thenValue));
+        }
+        if (elseValue != null) {
+            sql.append(" ELSE ").append(buildValue(elseValue));
+        }
+        sql.append(" END");
+        if (StringUtil.isNotBlank(alias)) {
+            return "(" + sql + ") AS " + dialect.wrap(alias);
+        }
+        return sql.toString();
+    }
+
+
+    @Override
+    String toConditionSql(List<QueryTable> queryTables, IDialect dialect) {
+        StringBuilder sql = new StringBuilder("CASE ");
+        sql.append(queryColumn.toSelectSql(queryTables, dialect));
+        for (When when : whens) {
+            sql.append(" WHEN ").append(buildValue(when.searchValue)).append(" THEN ").append(buildValue(when.thenValue));
+        }
+        if (elseValue != null) {
+            sql.append(" ELSE ").append(buildValue(elseValue));
+        }
+        sql.append(" END");
+        return "(" + sql + ")";
+    }
+
+
+    private String buildValue(Object value) {
+        if (value instanceof Number || value instanceof Boolean) {
+            return String.valueOf(value);
+        } else {
+            return "'" + value + "'";
+        }
+    }
+
+
+    void addWhen(When when) {
+        if (whens == null) {
+            whens = new ArrayList<>();
+        }
+        whens.add(when);
+    }
+
+    @Override
+    public QueryColumn as(String alias) {
+        this.alias = alias;
+        return this;
+    }
+
+    @Override
+    public <T> QueryColumn as(LambdaGetter<T> fn) {
+        return as(LambdaUtil.getFieldName(fn));
+    }
+
+    public static class When {
+        private Builder builder;
+        private Object searchValue;
+        private Object thenValue;
+
+        public When(Builder builder, Object searchValue) {
+            this.builder = builder;
+            this.searchValue = searchValue;
+        }
+
+        public Builder then(Object thenValue) {
+            this.thenValue = thenValue;
+            this.builder.caseQueryColumn.addWhen(this);
+            return builder;
+        }
+    }
+
+    public static class Builder {
+
+        private CaseSearchQueryColumn caseQueryColumn = new CaseSearchQueryColumn();
+
+        public Builder(QueryColumn queryColumn) {
+            this.caseQueryColumn.queryColumn = queryColumn;
+        }
+
+        public When when(Object searchValue) {
+            return new When(this, searchValue);
+        }
+
+        public Builder else_(Object elseValue) {
+            caseQueryColumn.elseValue = elseValue;
+            return this;
+        }
+
+        public CaseSearchQueryColumn end() {
+            return caseQueryColumn;
+        }
+    }
+}

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

@@ -0,0 +1,6 @@
+package com.mybatisflex.core.query;
+
+public interface HasParamsColumn {
+
+    Object[] getParamValues();
+}

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

@@ -183,8 +183,12 @@ public class QueryCondition implements Serializable {
             if (effectiveBefore != null) {
                 sql.append(effectiveBefore.connector);
             }
+            //列
             sql.append(getColumn().toConditionSql(queryTables, dialect));
+            //逻辑符号
             sql.append(" ").append(logic).append(" ");
+
+            //值（或者问号）
             if (value instanceof QueryColumn) {
                 sql.append(((QueryColumn) value).toConditionSql(queryTables, dialect));
             }

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

@@ -65,6 +65,14 @@ public class QueryMethods {
         return new DistinctQueryColumn(columns);
     }
 
+    public static CaseQueryColumn.Builder case_() {
+        return new CaseQueryColumn.Builder();
+    }
+
+    public static CaseSearchQueryColumn.Builder case_(QueryColumn queryColumn) {
+        return new CaseSearchQueryColumn.Builder(queryColumn);
+    }
+
     //CONVERT ( data_type [ ( length ) ] , expression [ , style ] )
     public static StringFunctionQueryColumn convert(String... params) {
         return new StringFunctionQueryColumn("CONVERT", params);

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

@@ -280,12 +280,12 @@ public class QueryWrapper extends BaseQueryWrapper<QueryWrapper> {
         return this;
     }
 
-    public QueryWrapper forUpdate(){
+    public QueryWrapper forUpdate() {
         addEndFragment("FOR UPDATE");
         return this;
     }
 
-    public QueryWrapper forUpdateNoWait(){
+    public QueryWrapper forUpdateNoWait() {
         addEndFragment("FOR UPDATE NOWAIT");
         return this;
     }
@@ -348,7 +348,7 @@ public class QueryWrapper extends BaseQueryWrapper<QueryWrapper> {
     }
 
     public QueryWrapper orderBy(String... orderBys) {
-        if(orderBys == null || orderBys.length == 0){
+        if (orderBys == null || orderBys.length == 0) {
             //ignore
             return this;
         }
@@ -395,16 +395,15 @@ public class QueryWrapper extends BaseQueryWrapper<QueryWrapper> {
 
         List<Object> columnValues = null;
         List<QueryColumn> selectColumns = getSelectColumns();
-        if (CollectionUtil.isNotEmpty(selectColumns)){
+        if (CollectionUtil.isNotEmpty(selectColumns)) {
             for (QueryColumn selectColumn : selectColumns) {
-                if (selectColumn instanceof SelectQueryColumn){
+                if (selectColumn instanceof HasParamsColumn) {
-                    QueryWrapper queryWrapper = ((SelectQueryColumn) selectColumn).getQueryWrapper();
+                    Object[] paramValues = ((HasParamsColumn) selectColumn).getParamValues();
-                    Object[] valueArray = queryWrapper.getValueArray();
+                    if (ArrayUtil.isNotEmpty(paramValues)) {
-                    if (ArrayUtil.isNotEmpty(valueArray)){
+                        if (columnValues == null) {
-                        if (columnValues == null){
                             columnValues = new ArrayList<>();
                         }
-                        columnValues.addAll(Arrays.asList(valueArray));
+                        columnValues.addAll(Arrays.asList(paramValues));
                     }
                 }
             }
@@ -466,7 +465,7 @@ public class QueryWrapper extends BaseQueryWrapper<QueryWrapper> {
         }
 
         Object[] returnValues = columnValues == null ? WrapperUtil.NULL_PARA_ARRAY : columnValues.toArray();
-        returnValues = tableValues != null ? ArrayUtil.concat(returnValues,tableValues.toArray()) : returnValues;
+        returnValues = tableValues != null ? ArrayUtil.concat(returnValues, tableValues.toArray()) : returnValues;
         returnValues = joinValues != null ? ArrayUtil.concat(returnValues, joinValues.toArray()) : returnValues;
         returnValues = ArrayUtil.concat(returnValues, paramValues);
 

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

@@ -17,12 +17,11 @@ package com.mybatisflex.core.query;
 
 import com.mybatisflex.core.dialect.IDialect;
 import com.mybatisflex.core.util.SqlUtil;
-
 import com.mybatisflex.core.util.StringUtil;
 
 import java.util.List;
 
-public class SelectQueryColumn extends QueryColumn {
+public class SelectQueryColumn extends QueryColumn implements HasParamsColumn {
 
     private QueryWrapper queryWrapper;
 
@@ -54,4 +53,9 @@ public class SelectQueryColumn extends QueryColumn {
     String toConditionSql(List<QueryTable> queryTables, IDialect dialect) {
         return super.toConditionSql(queryTables, dialect);
     }
+
+    @Override
+    public Object[] getParamValues() {
+        return queryWrapper.getValueArray();
+    }
 }

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

@@ -323,6 +323,43 @@ public class AccountSqlTester {
     }
 
 
+    @Test
+    public void testCase1() {
+        IDialect dialect = new CommonsDialectImpl();
+
+        QueryWrapper queryWrapper = QueryWrapper.create()
+                .select(ACCOUNT.ALL_COLUMNS,
+                        case_()
+                                .when(ACCOUNT.ID.eq(100)).then(100)
+                                .when(ACCOUNT.ID.ge(200)).then(200)
+                                .else_(300)
+                                .end().as("result"))
+                .from(ACCOUNT)
+                .and(ACCOUNT.USER_NAME.like("michael"));
+
+        String sql = dialect.forSelectByQuery(queryWrapper);
+        System.out.println(sql);
+    }
+
+    @Test
+    public void testCase2() {
+        IDialect dialect = new CommonsDialectImpl();
+
+        QueryWrapper queryWrapper = QueryWrapper.create()
+                .select(ACCOUNT.ALL_COLUMNS,
+                        case_(ACCOUNT.ID)
+                                .when(100).then(100)
+                                .when(200).then(200)
+                                .else_(300)
+                                .end().as("result"))
+                .from(ACCOUNT)
+                .and(ACCOUNT.USER_NAME.like("michael"));
+
+        String sql = dialect.forSelectByQuery(queryWrapper);
+        System.out.println(sql);
+    }
+
+
     @Test
     public void testLimitOffset() {