fix connection pool bug

hutool-db/src/main/java/cn/hutool/v7/db/ds/pooled/PooledConnection.java

@@ -35,6 +35,9 @@ import java.util.Properties;
 public class PooledConnection extends ConnectionWrapper {
 
 	private final PooledDataSource dataSource;
+	/**
+	 * 仅用于记录连接在池中的状态，如归还到池中为close状态，从池中拿出需调用{@link #open()}变为可用状态
+	 */
 	private boolean isClosed = false;
 
 	/**
@@ -99,6 +102,17 @@ public class PooledConnection extends ConnectionWrapper {
 		return this.isClosed;
 	}
 
+	/**
+	 * 打开连接<br>
+	 * 仅用于从连接池中拿出时调用，使链接变为可用。
+	 *
+	 * @return this
+	 */
+	PooledConnection open() {
+		this.isClosed = false;
+		return this;
+	}
+
 	/**
 	 * 销毁连接，即彻底关闭并丢弃连接
 	 */

hutool-db/src/main/java/cn/hutool/v7/db/ds/pooled/PooledDataSource.java

@@ -86,7 +86,7 @@ public class PooledDataSource extends AbstractDataSource {
 
 	@Override
 	public PooledConnection getConnection() throws SQLException {
-		return connPool.borrowObject();
+		return connPool.borrowObject().open();
 	}
 
 	@Override