Question

我在Netbeans中使用JNDI在Glassfish服务器中创建了一个JDBC连接池（jdbc/WILLIAMSON），我想在所有servlet中使用它，而不是在每个servlet中编写以下代码

     InitialContext context = new InitialContext();
        //The JDBC Data source that we just created
        DataSource datasource = (DataSource) 
         context.lookup("jdbc/WILLIAMSON");
         Connection connection = null;
          connection = ds.getConnection();

我创建了一个DBCONN类，并尝试在每个servlet中调用此类的对象，但是得到错误＆＃34;变量上下文可能尚未初始化＆＃34;。请参阅下面的代码：

       public final class DBCONN {    
       private static final InitialContext context;
       private static final DataSource datasource;
        static{              
          try {
              context = new InitialContext();
                 datasource=(DataSource) context.lookup("jdbc/WILLIAMSON");
          } catch (NamingException ex) {
              Logger.getLogger(DBCONN.class.getName()).log(Level.SEVERE, 
          null, ex);
          }
    }
   private DBCONN() {
      //  I am confused how to use this method, pls guide me
    }// ERROR HERE VARIABLE context MIGHT NOT HAVE BEEN INITIALIZED

    public static Connection getConnection() throws SQLException {
    return datasource.getConnection();
    }

    }

我在servlet HOME.java中调用datasource.getConnection()

       DBCONN datasource = new DBCONN();
        Connection connection = null;
        connection = datasource.getConnection();// I am accessing a static 
       method so warning coming accessing static method getConnection(), how 
        to avoid it???

Answer 1

将行更改为private static InitialContext context = null;。编译器警告您，在某些情况下，可能不会创建context。

Answer 2

static{
context = new InitialContext(); 
try { 
datasource=(DataSource) context.lookup("jdbc/WILLIAMSON");
} catch (NamingException ex) { 
Logger.getLogger(DBCONN.class.getName()).log(Level.SEVERE, null, ex);            }

JDBC连接池变量上下文可能尚未初始化

2 个答案: