update

README.md

@@ -2,12 +2,6 @@
 
 支持连表查询的[mybatis-plus](https://gitee.com/baomidou/mybatis-plus)
 
-## 运行环境
-
-* mysql8
-* jdk8
-* mybatis-plus 3.4.2
-
 ## 使用方法
 
 ### 方法一
@@ -47,6 +41,7 @@
 ## MyQuery用法
 
 ### 简单的3表查询
+
 ```java
 class test {
     @Resource
@@ -72,16 +67,14 @@ class test {
 对应sql
 
 ```sql
-SELECT 
+SELECT t.id,
-    t.id,
        t.name,
        t.sex,
        t.head_img,
        addr.tel,
        addr.address,
        a.province
-FROM 
+FROM user t
-    user t 
          LEFT JOIN user_address addr on t.id = addr.user_id
          RIGHT JOIN area a on addr.area_id = a.id
 WHERE (
@@ -92,6 +85,7 @@ WHERE (
 ```
 
 说明:
+
 * UserDTO.class 查询结果类(resultType)
 * selectAll(UserDO.class) 查询主表全部字段(主表实体类)
 * select() mp的select策略是覆盖,以最后一次为准,这里的策略是追加,可以一直select  
@@ -123,19 +117,16 @@ class test {
 对应sql
 
 ```sql
-SELECT 
+SELECT t.id,
-    t.id,
        t.name,
        t.sex,
        t.head_img,
        addr.tel,
        addr.address,
        a.province
-FROM 
+FROM user t
-user t 
          LEFT JOIN user_address addr on t.id = addr.user_id
-RIGHT JOIN area a on addr.area_id = a.id 
+         RIGHT JOIN area a on addr.area_id = a.id LIMIT ?,?
-LIMIT ?,?
 ```
 
 ### 还可以这么操作,但不建议
@@ -169,8 +160,7 @@ class test {
 对应sql
 
 ```sql
-SELECT 
+SELECT t.id,
-    t.id,
        t.name,
        t.sex,
        t.head_img,
@@ -178,8 +168,7 @@ SELECT
        addr.address,
        CASE t.sex WHEN '男' THEN '1' ELSE '0' END AS sex,
        sum(a.province)                           as province
-FROM 
+FROM user t
-user t 
          LEFT JOIN (select * from user_address) addr on t.id = addr.user_id
          RIGHT JOIN area a on addr.area_id = a.id
 WHERE (
@@ -201,12 +190,17 @@ class test {
     private UserMapper userMapper;
 
     void testJoin() {
-        List<UserDTO> list = userMapper.selectJoinList(UserDTO.class, new MyLambdaQueryWrapper<UserEntity>()
+        List<UserDTO> list = userMapper.selectJoinList(UserDTO.class,
-                        .selectAll(UserEntity.class)
+                new MyLambdaQueryWrapper<UserDO>()
-                        .leftJoin(UserEntity::getId, UserAddressEntity::getUserId,
+                        .selectAll(UserDO.class)
-                                r1 -> r1.select(UserAddressEntity::getAddress)
+                        .select(UserAddressDO::getTel)
-                                        .leftJoin(UserAddressEntity::getAreaId, AreaEntity::getId,
+                        .selectAs(UserAddressDO::getAddress, UserDTO::getUserAddress)
-                                                r2 -> r2.select(AreaEntity::getProvince))));
+                        .select(AreaDO::getProvince, AreaDO::getCity)
+                        .leftJoin(UserAddressDO.class, UserAddressDO::getUserId, UserDO::getId)
+                        .leftJoin(AreaDO.class, AreaDO::getId, UserAddressDO::getAreaId)
+                        .eq(true, UserDO::getId, 1)
+                        .like(true, UserAddressDO::getTel, "1")
+                        .gt(true, UserDO::getId, 5));
     }
 }
 ```
@@ -214,98 +208,71 @@ class test {
 对应sql
 
 ```sql
-SELECT t0.name,
+SELECT user.id,
-       t0.sex,
+       user.name,
-       t0.head_img,
+       user.sex,
-       t0.id,
+       user.head_img,
-       t1.address,
+       user_address.tel,
-       t2.province
+       user_address.address AS userAddress,
-FROM user t0
+       area.province,
-         LEFT JOIN user_address t1 ON t0.id = t1.user_id
+       area.city
-         LEFT JOIN area t2 ON t1.area_id = t2.id
+FROM user
-```
+         LEFT JOIN user_address ON user_address.user_id = user.id
-
+         LEFT JOIN area ON area.id = user_address.area_id
-sql -> 伪代码
-
-```java
-class test {
-    void testJoin() {
-        List<UserDTO> list = userMapper.selectJoinList(UserDTO.class, new MyLambdaQueryWrapper<user表>()
-                        .selectAll(user表实体类.class)//查询user表全部字段
-                        .leftJoin(user表on字段, user_address表on字段,
-                                user_address表对象 -> user_address表对象
-                                        .select(user_address表address字段)
-                                        .leftJoin(user_address表表的on字段, area表的on字段,
-                                                area表对象 -> area表对象.select(area表的province字段))));
-    }
-}
-```
-
-#### 字段别名,查询字段别名 head_img as userHeadImg
-
-```java
-class test {
-    @Resource
-    private UserMapper userMapper;
-
-    void testJoin() {
-        List<UserDTO> list = userMapper.selectJoinList(UserDTO.class, new MyLambdaQueryWrapper<UserEntity>()
-                        .as(UserEntity::getHeadImg, UserDTO::getUserHeadImg)
-                        .leftJoin(UserEntity::getId, UserAddressEntity::getUserId,
-                                right -> right.select(UserAddressEntity::getAddress, UserAddressEntity::getTel)));
-    }
-}
-```
-
-对应sql
-
-```sql
-SELECT t0.head_img AS userHeadImg,
-       t1.address,
-       t1.tel
-FROM user t0
-         LEFT JOIN user_address t1 ON t0.id = t1.user_id
-```
-
-#### 左连接 leftJoin(UserEntity::getId,UserAddressEntity::getUserId,right -> right)
-
-前连个参数是两个表的连接条件:  
-user left join user_address on user.id = User_address.user_id  
-第三个参数是右表wrapper对象,可以继续使用,以上方法.
-
-#### 条件查询
-
-```java
-class test {
-    @Resource
-    private UserMapper userMapper;
-
-    void testJoin() {
-        List<UserDTO> list = userMapper.selectJoinList(UserDTO.class, new MyLambdaQueryWrapper<UserEntity>()
-                        .selectAll(UserEntity.class)
-                        .leftJoin(UserEntity::getId, UserAddressEntity::getUserId,
-                                right -> right.select(UserAddressEntity::getAddress, UserAddressEntity::getTel))
-                        .eq(true, UserEntity::getId, 1)
-                        .like(UserAddressEntity::getTel, "1")
-                        .eq(UserEntity::getId, UserAddressEntity::getUserId));
-    }
-}
-```
-
-对应sql
-
-```sql
-SELECT t0.name,
-       t0.sex,
-       t0.head_img,
-       t0.id,
-       t1.address,
-       t1.tel
-FROM user t0
-         LEFT JOIN user_address t1 ON t0.id = t1.user_id
 WHERE (
-              t0.id = ?
+              user.id = ?
-              AND t1.tel LIKE ?
+              AND user_address.tel LIKE ?
-              AND t0.id = t1.user_id)
+              AND user.id > ?)
 ```
 
+说明:
+
+* UserDTO.class 查询结果返回类(resultType)
+* selectAll() 查询指定实体类的全部字段
+* select() 查询指定的字段,支持可变参数,同意个select只能查询相同表的字段  
+  故将UserAddressDO和AreaDO分开为连个select
+* selectAs() 字段别名查询,用于数据库字段与业务实体类属性名不一致时使用
+* leftJoin() 参数说明  
+  第一个参数:参与连表的实体类class  
+  第二个参数数:连表的ON字段,这个属性必须是第一个参数实体类的属性  
+  第三个参数:参与连表的另一个实体类属性
+* 条件查询,可以查询主表以及参与连接的所有表的字段,全部调用mp原生的方法,正常使用没有sql注入风险
+
+#### 分页查询
+
+```java
+class test {
+    @Resource
+    private UserMapper userMapper;
+
+    void testJoin() {
+        IPage<UserDTO> iPage = userMapper.selectJoinPage(new Page<>(2, 10), UserDTO.class,
+                new MyLambdaQueryWrapper<UserDO>()
+                        .selectAll(UserDO.class)
+                        .select(UserAddressDO::getTel)
+                        .selectAs(UserAddressDO::getAddress, UserDTO::getUserAddress)
+                        .select(AreaDO::getProvince, AreaDO::getCity)
+                        .leftJoin(UserAddressDO.class, UserAddressDO::getUserId, UserDO::getId)
+                        .leftJoin(AreaDO.class, AreaDO::getId, UserAddressDO::getAreaId));
+    }
+}
+```
+
+对应sql
+
+```mysql
+SELECT user.id,
+       user.name,
+       user.sex,
+       user.head_img,
+       user_address.tel,
+       user_address.address AS userAddress,
+       area.province,
+       area.city
+FROM user
+         LEFT JOIN user_address ON user_address.user_id = user.id
+         LEFT JOIN area ON area.id = user_address.area_id
+LIMIT ?,?
+```
+
+

src/main/java/com/github/mybatisplus/wrapper/MyAbstractLambdaWrapper.java

@@ -14,6 +14,7 @@ import org.apache.ibatis.reflection.property.PropertyNamer;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 
 import static java.util.stream.Collectors.joining;
 
@@ -93,8 +94,9 @@ public abstract class MyAbstractLambdaWrapper<T, Children extends MyAbstractLamb
 
     private ColumnCache getColumnCache(String fieldName, Class<?> lambdaClass) {
         ColumnCache columnCache = columnMap.get(LambdaUtils.formatKey(fieldName));
-        Assert.notNull(columnCache, "can not find lambda cache for this property [%s] of entity [%s]",
+        if (Objects.isNull(columnCache)) {
-                fieldName, lambdaClass.getName());
+            columnCache = new ColumnCache(fieldName, null);
+        }
         return columnCache;
     }
 

src/main/java/com/github/mybatisplus/wrapper/MyLambdaQueryWrapper.java

@@ -118,10 +118,20 @@ public class MyLambdaQueryWrapper<T> extends MyAbstractLambdaWrapper<T, MyLambda
     public final <S, X> MyLambdaQueryWrapper<T> selectAs(SFunction<S, ?> columns, SFunction<X, ?> alias) {
         Class<S> clazz = MyLambdaUtils.getEntityClass(columns);
         TableInfo info = TableInfoHelper.getTableInfo(clazz);
+        Assert.notNull(info, "table can not be find for lambda");
         selectColumns.add(new SelectColumn(clazz, info.getTableName(), MyLambdaUtils.getColumn(columns), MyLambdaUtils.getName(alias)));
         return typedThis;
     }
 
+    public final MyLambdaQueryWrapper<T> selectAll(Class<?> clazz) {
+        TableInfo info = TableInfoHelper.getTableInfo(clazz);
+        Assert.notNull(info, "table can not be find -> %s", clazz);
+        selectColumns.add(new SelectColumn(clazz, info.getTableName(), info.getKeyColumn(), null));
+        info.getFieldList().forEach(c ->
+                selectColumns.add(new SelectColumn(clazz, info.getTableName(), c.getColumn(), null)));
+        return typedThis;
+    }
+
     @Override
     public String getSqlSelect() {
         if (StringUtils.isBlank(sqlSelect.getStringValue())) {