事务处理中如何获取同一个connection 对象

运用线程内部的map属性，将对象绑定到ThreadLocal中：

具体实现:

1.新建一个绑定Connection对象的单例类

public class ConnectionBind {
    private ConnectionBind(){}
    private static ConnectionBind instance=new ConnectionBind()；
    public static ConnectionBind getInstance() {
        return instance;
    }    
    private ThreadLocal<Connection> threadLocal=new ThreadLocal<>();
    
    //线程绑定
    public void bind(Connection connection){
        threadLocal.set(connection);
    }
    
    //获取绑定的线程对象
    public Connection get(){
        return threadLocal.get();
    }
    
    //解出绑定
    public void remove(){
        threadLocal.remove();
    }    
}

2.新建一个ThreadLocationFilter过滤器，对所有的请求过滤，在doFilter方法中做如下实现：

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        Connection connection=null;
        try {
            //1.获取连接
            connection =JdbcUtils.getConnection();
            
            //2.开启事务
            connection.setAutoCommit(false);
            
            //3.利用ThreadLocal把当前连接和当前线程绑定
            ConnectionBind.getInstance().bind(connection);
            
            //4.把请求转给目标Servlet
            chain.doFilter(request, response);

            //5.提交事务
            connection.commit();
            
        } catch (Exception e) {
            //6.回滚事务
            try {
                connection.rollback();
            } catch (SQLException e1) {
                e1.printStackTrace();
            } 
　　　　　　　//重定向到错误页面           
            HttpServletRequest request2=(HttpServletRequest) request;
            HttpServletResponse response2=(HttpServletResponse) response;
            response2.sendRedirect(request2.getContextPath()+"/error-1.jsp");
        }finally{
            //7.解出绑定
            ConnectionBind.getInstance().remove();
            
            //8.关闭数据库连接
            JdbcUtils.releaseConnection(connection);
        }
        
    }

3.获取同一个Connection连接对象

Connection connection=null;
connection=ConnectionBind.getInstance().get();