事務處理中如何獲取同一個connection 對象

運用線程內部的map屬性，將對象綁定到ThreadLocal中：

具體實現:

1.新建一個綁定Connection對象的單例類

public class ConnectionBind {
    private ConnectionBind(){}
    private static ConnectionBind instance=new ConnectionBind()；
    public static ConnectionBind getInstance() {
        return instance;
    }    
    private ThreadLocal<Connection> threadLocal=new ThreadLocal<>();
    
    //線程綁定
    public void bind(Connection connection){
        threadLocal.set(connection);
    }
    
    //獲取綁定的線程對象
    public Connection get(){
        return threadLocal.get();
    }
    
    //解出綁定
    public void remove(){
        threadLocal.remove();
    }    
}

2.新建一個ThreadLocationFilter過濾器，對所有的請求過濾，在doFilter方法中做如下實現：

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        Connection connection=null;
        try {
            //1.獲取連接
            connection =JdbcUtils.getConnection();
            
            //2.開啟事務
            connection.setAutoCommit(false);
            
            //3.利用ThreadLocal把當前連接和當前線程綁定
            ConnectionBind.getInstance().bind(connection);
            
            //4.把請求轉給目標Servlet
            chain.doFilter(request, response);

            //5.提交事務
            connection.commit();
            
        } catch (Exception e) {
            //6.回滾事務
            try {
                connection.rollback();
            } catch (SQLException e1) {
                e1.printStackTrace();
            } 
　　　　　　　//重定向到錯誤頁面           
            HttpServletRequest request2=(HttpServletRequest) request;
            HttpServletResponse response2=(HttpServletResponse) response;
            response2.sendRedirect(request2.getContextPath()+"/error-1.jsp");
        }finally{
            //7.解出綁定
            ConnectionBind.getInstance().remove();
            
            //8.關閉數據庫連接
            JdbcUtils.releaseConnection(connection);
        }
        
    }

3.獲取同一個Connection連接對象

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