JSF启动数据库报错

Question

高手帮我分析下  我的一个受管bean类实现了对数据库查询操作，但是登陆系统的时候tomcat报错
exception javax.servlet.ServletException
javax.faces.webapp.FacesServlet.service(FacesServlet.java:256)root cause java.lang.NullPointerException
org.jia.EManage.web.SelectExperimentBean.getAdminExperiment(SelectExperimentBean.java:85)其中报错的85行代码为
public ArrayList<Experiment> getAdminExperiment()throws Exception
  {
  return experimentDaoImpl.getAdminExperiment();
  }其中具体的数据库操作方法代码为
public ArrayList<Experiment> getAdminExperiment() throws Exception{
ArrayList<Experiment> result=new ArrayList<Experiment>();
Connection conn=null;
PreparedStatement stmt=null;
ResultSet rs=null;
try{
conn=DBConn.getCon();
String sql="select * from experiment where status = ?";
stmt=conn.prepareStatement(sql);
stmt.setInt(1, 0); while(rs.next()){
//查询结果转化为Experiment对象
Experiment experiment=new Experiment(); experiment.setId(rs.getInt("id"));
experiment.setAim(rs.getString("aim"));
experiment.setDescribe(rs.getString("describes"));
experiment.setComments(rs.getString("comments"));
experiment.setName(rs.getString("name"));
experiment.setStatus(rs.getInt("status"));
experiment.setInitiatedId(rs.getInt("initiatedId"));

result.add(experiment);
}
//取得初始状态的实验列表

}catch(SQLException sqle){
throw new SQLException("select data exception:"+
sqle.getMessage());
}catch(Exception e){ }
return result;

}

Answer 1

rs是在什么地方付值的?
应该有rs=stmt.executeQuery(sql);