Vaadin从SQLContainer填充网格

Question

我需要帮助用来自SQLContainer的数据填充Grid。我有以下代码：

 public void createConnetionDB(){
            try {
                connectionPool = new SimpleJDBCConnectionPool(
                         "com.mysql.jdbc.Driver",
                         "jdbc:mysql://localhost:3306/test", "root", "root", 2, 5);

            }
            catch(Exception e){
                text.setCaption(e.toString()); 

            }
      }

public SQLContainer initSQLContainer(){
   TableQuery tq = null; 
   tq = new TableQuery("articles", connectionPool);
   tq.setVersionColumn("OPTLOCK");
   SQLContainer articleContainer  = new SQLContainer(tq);

   return articleContainer; 

}

Grid articles = new Grid(); 
articles.setContainerDataSource(initSQLContainer()); 

运行它时我得到nullpointerexception。怎么了？

提前致谢

Answer 1

由于变量connectionPool为null，您会收到异常。我想你忘了打createConnectionDB()。

试试这样：

public SQLContainer initSQLContainer() {

   createConnetionDB();  

   TableQuery tq = new TableQuery("articles", connectionPool);
   tq.setVersionColumn("OPTLOCK");
   SQLContainer articleContainer  = new SQLContainer(tq);

   return articleContainer; 

}