Question

当我制作DAO Serializable时我有DAO我得到例外：

 Cannot serialize session attribute com.sun.faces.renderkit.ServerSideStateHelper.LogicalViewMap for session C354B1B6053088CBB8E8A933E5F8EAE0
    java.io.NotSerializableException: org.apache.tomcat.dbcp.dbcp.PoolingDataSource$PoolGuardConnectionWrapper

我的DAO：

public boolean getConnection() {
        try {
            InitialContext context = new InitialContext();
            DataSource dataSource = (DataSource) context.lookup("java:/comp/env/jdbc/Orcl");
            connection = dataSource.getConnection();
            return true;
        } catch (SQLException ex) {
            Logger.getLogger(KPIDAO.class.getName()).log(Level.SEVERE, null, ex);
            return false;
        } catch (NamingException ex) {
            Logger.getLogger(KPIDAO.class.getName()).log(Level.SEVERE, null, ex);
            return false;
        }
    }

在控制器（@ViewScoped）中：

KPIDAO kpiDAO = new KPIDAO();

context.xml中

<Resource 
        name="jdbc/Orcl" 
        auth="Container"
        type="javax.sql.DataSource" 
        username="username" 
        password="password"
        driverClassName="oracle.jdbc.OracleDriver" 
        url="jdbc:oracle:thin:@192.168.1.10:1521:XE"
        maxActive="8" 
   />

什么是正确的解决方案？

Answer 1

例如

@ViewScoped
public class ViewBean implements Serializable{
  private transient KPIDAO kpiDAO = //get singleton instance from factory
  //also dont keep connection object as instance variable, fetch it from pool in methods and perform db operations.

  private void readObject(java.io.ObjectInputStream stream)
        throws java.io.IOException, ClassNotFoundException
    {
        stream.defaultReadObject();

        // assign reference manually.
        this.kpiDAO  =  //get from factory;
    }

private void writeObject(java.io.ObjectOutputStream stream)
        throws java.io.IOException
    {

        stream.defaultWriteObject();
    }
}

注意：如果您将连接对象从实例变量移动到本地方法变量，你也不需要上面的代码。

<强>更新

从您的代码段和例外

connection = dataSource.getConnection();

它似乎是一个实例变量。

即

public class Dao {
 private Connection connection; //instance variable
}

将其更改为

public class Dao {

 public List<Bean> getResult(){
  //local method variable
  Connection connection = //get from pool
  //perform db operation with connection object
 }

}

Answer 2

您不应该在会话中存储对PoolingDataSource的引用，因为PoolingDataSource不可序列化。我建议你把它存放在其他地方，例如在应用程序上下文中。

DBCP中的非序列化异常

2 个答案: