!293 修复多数据源多线程切换问题

Merge pull request !293 from life/main

docs/zh/core/tx.md

@@ -244,3 +244,46 @@ seata:
 
 [mybatis-flex-spring-boot-seata-demo](https://gitee.com/mybatis-flex/mybatis-flex-samples/tree/master/mybatis-flex-spring-boot-seata-demo) : Seata 官方 demo 与 flex 结合。
 
+
+## 子父线程同时访问一个ThreadLocal访问的场景
+考虑到某些场景下，子父线程会同时访问父线程进行传递值进行切换数据源的场景，提供了以下的支持
+比如如下的代码：
+```java
+public static void main(String[]args){
+        //线程1
+        //进行数据库操作读取 ds1
+        //切换数据源2
+        DataSourceKey.use("ds2");
+        new Thread(() -> {
+            //查询数据源 ds2
+            //实际在线程2并不是ds2而是ds1
+        }).start();
+}
+```
+此类场景进行如下的方案进行修改
+1. 使用可以跨越线程池的`ThreadLocal`比如阿里的`transmittable-thread-local`
+导入如下的包
+```xml
+     <dependency>
+            <groupId>com.alibaba</groupId>
+            <artifactId>transmittable-thread-local</artifactId>
+            <version>2.14.2</version>
+        </dependency>
+```
+2. 对切换的源码进行修改
+```java
+public static void main(String[]args){
+        DataSourceKey.setAnnotationKeyThreadLocal(new TransmittableThreadLocal<>());
+        DataSourceKey.setManualKeyThreadLocal(new TransmittableThreadLocal<>());
+        //线程1
+        //进行数据库操作读取 ds1
+        //切换数据源2
+        DataSourceKey.use("ds2");
+        new Thread(() -> {
+            //查询数据源 ds2
+            //实际在线程2使用的就是ds2
+        }).start();
+}
+```
+### 扩展阅读
+[transmittable-thread-local](https://github.com/alibaba/transmittable-thread-local) 可以不侵入进行代码原线程的替换

mybatis-flex-core/pom.xml

@@ -70,6 +70,7 @@
             <scope>compile</scope>
             <optional>true</optional>
         </dependency>
+
         <!--optional end-->
 
         <dependency>

mybatis-flex-core/src/main/java/com/mybatisflex/core/datasource/DataSourceKey.java

@@ -25,12 +25,12 @@ public class DataSourceKey {
     /**
      * 通过注解设置的 key
      */
-    private static final ThreadLocal<String> annotationKeyThreadLocal = new ThreadLocal<>();
+    private static ThreadLocal<String> annotationKeyThreadLocal = new ThreadLocal<>();
 
     /**
      * 通过手动编码指定的 key
      */
-    private static final ThreadLocal<String> manualKeyThreadLocal = new ThreadLocal<>();
+    private static ThreadLocal<String> manualKeyThreadLocal = new ThreadLocal<>();
 
     public static String manualKey;
 
@@ -81,4 +81,11 @@ public class DataSourceKey {
         return key != null ? key : annotationKeyThreadLocal.get();
     }
 
+    public static void setAnnotationKeyThreadLocal(ThreadLocal<String> annotationKeyThreadLocal) {
+        DataSourceKey.annotationKeyThreadLocal = annotationKeyThreadLocal;
+    }
+
+    public static void setManualKeyThreadLocal(ThreadLocal<String> manualKeyThreadLocal) {
+        DataSourceKey.manualKeyThreadLocal = manualKeyThreadLocal;
+    }
 }

mybatis-flex-test/mybatis-flex-native-test/pom.xml

@@ -108,6 +108,12 @@
 <!--            <scope>test</scope>-->
 <!--        </dependency>-->
 
+        <dependency>
+            <groupId>com.alibaba</groupId>
+            <artifactId>transmittable-thread-local</artifactId>
+            <version>2.14.2</version>
+        </dependency>
+
 
         <dependency>
             <groupId>org.assertj</groupId>

mybatis-flex-test/mybatis-flex-native-test/src/main/java/com/mybatisflex/test/MultiThreadsTest.java

@@ -0,0 +1,69 @@
+package com.mybatisflex.test;
+
+import com.alibaba.ttl.TransmittableThreadLocal;
+import com.mybatisflex.core.MybatisFlexBootstrap;
+import com.mybatisflex.core.audit.AuditManager;
+import com.mybatisflex.core.audit.ConsoleMessageCollector;
+import com.mybatisflex.core.audit.MessageCollector;
+import com.mybatisflex.core.datasource.DataSourceKey;
+import com.mybatisflex.core.row.Db;
+import com.mybatisflex.core.row.Row;
+import com.mybatisflex.core.row.RowUtil;
+import com.zaxxer.hikari.HikariDataSource;
+import java.util.List;
+import javax.sql.DataSource;
+import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
+import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseType;
+
+/**
+ * @author life
+ */
+public class MultiThreadsTest {
+
+    public static void main(String[] args) {
+        DataSourceKey.setAnnotationKeyThreadLocal(new TransmittableThreadLocal<>());
+        DataSourceKey.setManualKeyThreadLocal(new TransmittableThreadLocal<>());
+        DataSource dataSource = new EmbeddedDatabaseBuilder()
+            .setType(EmbeddedDatabaseType.H2)
+            .setName("db1")
+            .addScript("schema.sql")
+            .addScript("data.sql")
+            .build();
+
+        HikariDataSource dataSource2 = new HikariDataSource();
+        dataSource2.setJdbcUrl("jdbc:mysql://127.0.0.1:3306/flex_test?characterEncoding=utf-8");
+        dataSource2.setUsername("root");
+        dataSource2.setPassword("131496");
+
+        MybatisFlexBootstrap.getInstance()
+            .setDataSource(dataSource)
+            .addMapper(AccountMapper.class)
+            .addDataSource("ds2", dataSource2)
+            .start();
+
+        //开启审计功能
+        AuditManager.setAuditEnable(true);
+
+        //设置 SQL 审计收集器
+        MessageCollector collector = new ConsoleMessageCollector();
+        AuditManager.setMessageCollector(collector);
+
+        //默认查询 db1
+        System.out.println("\n------ds1");
+        List<Row> rows1 = Db.selectAll(null, "tb_account");
+        RowUtil.printPretty(rows1);
+
+        System.out.println("\n------ds2");
+        DataSourceKey.use("ds2");
+        new Thread(() -> {
+            //查询数据源 ds2
+            System.out.println("\n------Thread-ds2");
+            List<Row> rows = Db.selectAll(null, "tb_account");
+            RowUtil.printPretty(rows);
+        }).start();
+
+
+
+    }
+
+}