From 81cea3a5b222a771e857311ea739f9e6c2fc8d98 Mon Sep 17 00:00:00 2001
From: admin <570810310@qq.com>
Date: Mon, 22 Feb 2021 15:54:42 +0800
Subject: [PATCH] 1.0.9

---
 .../com/github/yulichang/common/README.md     |  2 +
 .../support/AliasLambdaQueryWrapper.java      | 32 ++++++++
 .../common/support/AliasQueryWrapper.java     | 30 +++++++
 .../github/yulichang/common/support/README.md | 82 +++++++++++++++++++
 4 files changed, 146 insertions(+)
 create mode 100644 src/main/java/com/github/yulichang/common/support/AliasLambdaQueryWrapper.java
 create mode 100644 src/main/java/com/github/yulichang/common/support/AliasQueryWrapper.java
 create mode 100644 src/main/java/com/github/yulichang/common/support/README.md

diff --git a/src/main/java/com/github/yulichang/common/README.md b/src/main/java/com/github/yulichang/common/README.md
index 481f406..705f7a7 100644
--- a/src/main/java/com/github/yulichang/common/README.md
+++ b/src/main/java/com/github/yulichang/common/README.md
@@ -2,6 +2,8 @@
 
 [官方自定义sql](https://mp.baomidou.com/guide/wrapper.html#%E4%BD%BF%E7%94%A8-wrapper-%E8%87%AA%E5%AE%9A%E4%B9%89sql)
 
+官方提供的自定义sql不支持表别名和多实体泛型,扩展能力有限,对此就行了优化
+
 ### 使用方法
 
 #### 如需单独使用 请拷贝以下6个类
diff --git a/src/main/java/com/github/yulichang/common/support/AliasLambdaQueryWrapper.java b/src/main/java/com/github/yulichang/common/support/AliasLambdaQueryWrapper.java
new file mode 100644
index 0000000..1663b15
--- /dev/null
+++ b/src/main/java/com/github/yulichang/common/support/AliasLambdaQueryWrapper.java
@@ -0,0 +1,32 @@
+package com.github.yulichang.common.support;
+
+import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
+import com.baomidou.mybatisplus.core.toolkit.StringPool;
+import com.baomidou.mybatisplus.core.toolkit.StringUtils;
+import com.baomidou.mybatisplus.core.toolkit.support.SFunction;
+
+/**
+ * 字段添加别名
+ *
+ * @author yulichang
+ */
+public class AliasLambdaQueryWrapper<T> extends LambdaQueryWrapper<T> {
+    /**
+     * 字段别名
+     */
+    private String alias;
+
+    public AliasLambdaQueryWrapper<T> setAlias(String alias) {
+        this.alias = alias;
+        return this;
+    }
+
+    /**
+     * 重写字段序列化方法
+     */
+    @Override
+    protected String columnToString(SFunction<T, ?> column, boolean onlyColumn) {
+        String as = super.columnToString(column, onlyColumn);
+        return StringUtils.isBlank(alias) ? as : (alias + StringPool.DOT + as);
+    }
+}
diff --git a/src/main/java/com/github/yulichang/common/support/AliasQueryWrapper.java b/src/main/java/com/github/yulichang/common/support/AliasQueryWrapper.java
new file mode 100644
index 0000000..c4b5eed
--- /dev/null
+++ b/src/main/java/com/github/yulichang/common/support/AliasQueryWrapper.java
@@ -0,0 +1,30 @@
+package com.github.yulichang.common.support;
+
+import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
+import com.baomidou.mybatisplus.core.toolkit.StringPool;
+import com.baomidou.mybatisplus.core.toolkit.StringUtils;
+
+/**
+ * 字段添加别名
+ *
+ * @author yulichang
+ */
+public class AliasQueryWrapper<T> extends QueryWrapper<T> {
+    /**
+     * 字段别名
+     */
+    private String alias;
+
+    public AliasQueryWrapper<T> setAlias(String alias) {
+        this.alias = alias;
+        return this;
+    }
+
+    /**
+     * 重写字段序列化方法
+     */
+    @Override
+    protected String columnToString(String column) {
+        return StringUtils.isBlank(alias) ? column : (alias + StringPool.DOT + column);
+    }
+}
diff --git a/src/main/java/com/github/yulichang/common/support/README.md b/src/main/java/com/github/yulichang/common/support/README.md
new file mode 100644
index 0000000..c708b4f
--- /dev/null
+++ b/src/main/java/com/github/yulichang/common/support/README.md
@@ -0,0 +1,82 @@
+## 别名wrapper用法
+
+[官方自定义sql](https://mp.baomidou.com/guide/wrapper.html#%E4%BD%BF%E7%94%A8-wrapper-%E8%87%AA%E5%AE%9A%E4%B9%89sql)
+
+官方提供的自定义sql不支持表别名和多实体泛型,扩展能力有限,对此就行了优化  
+
+原理:  
+AliasQueryWrapper继承QueryWrapper  
+AliasLambdaQueryWrapper继承LambdaQueryWrapper  
+这两个类重写了父类字段序列化方法columnToString,添加别名
+
+### 使用方法
+
+#### AliasLambdaQueryWrapper
+
+注解:
+
+```java
+
+@Mapper
+public interface UserMapper extends BaseMapper<UserDO> {
+
+    @Select("select u.*,ua.tel from user u left join user_address ua on u.id = ua.user_id ${ew.customSqlSegment}")
+    UserDTO userLeftJoin(@Param(Constants.WRAPPER) Wrapper<?> queryWrapper);
+}
+```
+
+或者xml
+
+```
+<select id="userLeftJoin" resultType="UserDTO">
+    select 
+        u.*, 
+        ua.tel
+    from 
+        user u
+        left join user_address ua on u.id = ua.user_id
+    ${ew.customSqlSegment}
+</select>
+```
+
+使用wrapper:
+
+```java
+class MpJoinTest {
+    @Resource
+    private UserMapper userMapper;
+
+    @Test
+    void test() {
+        UserDTO userDTO = userMapper.userLeftJoin(new AliasLambdaQueryWrapper<UserDO>()
+                .setAlias("u")                //指定别名,要与注解或xml中的别名保持一致
+                .eq(UserDO::getId, "1")
+                .like(UserDO::getSex, "3"));
+    }
+}
+```
+
+对应sql:
+
+```
+select 
+    u.*,
+    ua.tel 
+from user u 
+    left join user_address ua on u.id = ua.user_id 
+WHERE (
+    u.id = ? 
+    AND u.sex LIKE ?)
+```
+
+#### AliasQueryWrapper
+
+mybatis-plus原生的QueryWrapper也是可以实现别名的,但是没有统一的转换方法,开发时容易忽略
+
+AliasQueryWrapper.setAlias("u").eq("id", 1);  
+等效与  
+QueryWrapper.eq("u.id", 1);  
+
+AliasQueryWrapper别名一次设置全局通用,不需要每个字段都加别名
+
+QQ群:1022221898
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