From cd0a3d0f4948bb3395f7b7237850a7057e8f86c3 Mon Sep 17 00:00:00 2001
From: admin <570810310@qq.com>
Date: Mon, 22 Mar 2021 10:44:56 +0800
Subject: [PATCH] =?UTF-8?q?=E6=96=B0=E5=A2=9Eselect=E5=88=AB=E5=90=8D?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../alias/AliasLambdaQueryWrapper.java        | 64 ++++++++++++++++++-
 1 file changed, 62 insertions(+), 2 deletions(-)

diff --git a/src/main/java/com/github/yulichang/common/support/alias/AliasLambdaQueryWrapper.java b/src/main/java/com/github/yulichang/common/support/alias/AliasLambdaQueryWrapper.java
index 73a704a..f1e0a25 100644
--- a/src/main/java/com/github/yulichang/common/support/alias/AliasLambdaQueryWrapper.java
+++ b/src/main/java/com/github/yulichang/common/support/alias/AliasLambdaQueryWrapper.java
@@ -1,24 +1,42 @@
 package com.github.yulichang.common.support.alias;
 
 import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
+import com.baomidou.mybatisplus.core.metadata.TableInfo;
+import com.baomidou.mybatisplus.core.metadata.TableInfoHelper;
+import com.baomidou.mybatisplus.core.toolkit.Assert;
+import com.baomidou.mybatisplus.core.toolkit.CollectionUtils;
 import com.baomidou.mybatisplus.core.toolkit.StringPool;
 import com.baomidou.mybatisplus.core.toolkit.StringUtils;
 import com.baomidou.mybatisplus.core.toolkit.support.SFunction;
 
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.stream.Collectors;
+
 /**
  * 字段添加别名
  * 使用方法:
  * <p>
- * select t.* from table t ${ew.customSqlSegment("t")}
+ * select ${ew.aliasColumn("table","t")} from table t ${ew.customSqlSegment("t")}
+ * </p>
+ * 对应sql
  * <p>
+ * select t.id,t.sex from table t where t.id = ? and t.sex = ?
+ * </p>
  * 注意:
- * 官方的自定义sql是ew.customSqlSegment,不带括号,会调用getCustomSqlSegment方法
+ * 官方的自定义sql是ew.customSqlSegment,不带括号,会调用getCustomSqlSegment()方法
  * 带别名的是 ew.customSqlSegment("t") 带括号
  * 括号中的别名必须带双引号
  *
  * @author yulichang
  */
 public class AliasLambdaQueryWrapper<T> extends LambdaQueryWrapper<T> {
+
+    /**
+     * 别名查询字段缓存
+     */
+    private static final Map<Class<?>, Map<String, String>> ALIAS_COLUMN_CACHE = new ConcurrentHashMap<>();
+
     /**
      * 字段别名
      */
@@ -33,8 +51,50 @@ public class AliasLambdaQueryWrapper<T> extends LambdaQueryWrapper<T> {
         return StringUtils.isBlank(alias) ? as : (alias + StringPool.DOT + as);
     }
 
+    /**
+     * ew.customSqlSegment("t")
+     */
     public String customSqlSegment(String alias) {
         this.alias = alias;
         return super.getCustomSqlSegment();
     }
+
+    /**
+     * ew.customSqlSegment("table_name", "t")
+     *
+     * @param tableName 数据库表名
+     * @param alias     别名
+     */
+    public String aliasColumn(String tableName, String alias) {
+        TableInfo tableInfo = TableInfoHelper.getTableInfo(tableName);
+        Assert.notNull(tableInfo, "未找到对应的表 -> %s", tableName);
+        Assert.isTrue(StringUtils.isNotBlank(alias), "别名不能为空");
+
+        this.alias = alias;
+        Map<String, String> aliasMap = ALIAS_COLUMN_CACHE.get(tableInfo.getEntityType());
+        if (CollectionUtils.isEmpty(aliasMap)) {
+            aliasMap = new ConcurrentHashMap<>();
+            String s = concat(tableInfo, alias);
+            aliasMap.put(alias, s);
+            ALIAS_COLUMN_CACHE.put(tableInfo.getEntityType(), aliasMap);
+            return s;
+        } else {
+            if (!aliasMap.containsKey(alias)) {
+                String s = concat(tableInfo, alias);
+                aliasMap.put(alias, s);
+                return s;
+            } else {
+                return aliasMap.get(alias);
+            }
+        }
+    }
+
+    private String concat(TableInfo tableInfo, String alias) {
+        String s = tableInfo.getFieldList().stream().map(
+                i -> alias + StringPool.DOT + i.getColumn()).collect(Collectors.joining(StringPool.COMMA));
+        if (tableInfo.havePK()) {
+            s = alias + StringPool.DOT + tableInfo.getKeyColumn() + StringPool.COMMA + s;
+        }
+        return s;
+    }
 }