我在部署ZK 时遇到了一些错误
Jan 16, 2012 5:00:59 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [zkLoader] in context with path [/ZK509App6] threw exception
java.lang.NullPointerException
at controller.jurnal.JournalController.<init>(JournalController.java:39)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
这是我的JournalController.java类
public class JournalController extends GenericForwardComposer {
private Listbox listlk;
private Datebox datebox;
private koneksi k;
private Connection c;
private SimpleDateFormat sdf;
private Button pilih;
private Date dates;
private jurnalDAO jd = new jurnalDAO(k.getConnection(), dates);
public JournalController() {
}
public void onClick$pilih(Event e) throws Exception, SQLException {
try {
Date d = datebox.getValue();
d = dates;
ForwardEvent forwardEvt = (ForwardEvent) e;
Listbox Listlk = (Listbox) forwardEvt.getOrigin().getTarget();
} catch (Exception a) {
a.printStackTrace();
}
}
public List<Jurnal_tbl> getAllEvents() throws SQLException, Exception {
return jd.getLKeuangan();
}
}
(JournalController.java:39)的行是private jurnalDAO jd=新jurnal DAO(k.getConnection(),日期)
对于引用,这是DAO类
public class jurnalDAO {
private Connection conn;
private Date tanggal;
public jurnalDAO(Connection conn, Date dates) {
this.conn = conn;
this.tanggal = dates;
}
public List<Jurnal_tbl> getLKeuangan() throws SQLException, Exception {
PreparedStatement ps = null;
try {
List<Jurnal_tbl> llk = new ArrayList<Jurnal_tbl>();
System.out.println("test1");
String sql = "SELECT * from public.jurnal where tanggal = ?";
ps = conn.prepareStatement(sql);
ps.setDate(1, new java.sql.Date(tanggal.getTime()));
System.out.println(ps.toString());;
ResultSet rs = ps.executeQuery();
Jurnal_tbl jt;
while (rs.next()) {
// llk.add(new Jurnal_tbl(rs.getString("kd_jurnal"), rs.getString("no_trans"), rs.getString("tanggal"), rs.getString("account"), rs.getString("descript"), rs.getString("dc"), rs.getDouble("amount"), rs.getString("no_item")));
jt = new Jurnal_tbl();
jt.setKode(rs.getString("kd_jurnal"));
jt.setTransaksi(rs.getString("no_trans"));
jt.setTanggal(rs.getString("tanggal"));
jt.setAkun(rs.getString("akun"));
jt.setDeskripsi(rs.getString("descript"));
jt.setDC(rs.getString("dc"));
jt.setAmount(rs.getDouble("amount"));
jt.setItem(rs.getString("no_item"));
llk.add(jt);
}
rs.close();
return llk;
} finally {
}
}
}
请帮帮我,伙计们,T这是我学士学位的最后一个项目
您正在调用k.getConnection()
,但从未初始化过k
,因此它将具有默认值null
。这必然会抛出NullPointerException
。您期望在哪个对象上调用getConnection()
?
顺便说一句,值得注意的是名称:
k
对于实例变量来说是一个非常没有意义的名称- 你在"日记"one_answers"陪审团"之间不一致
- 类型名称
koneksi
不遵循Java命名约定(大写) - 变量名
Listlk
不遵循Java命名约定(大写) - 类型名称
Jurnal_tbl
不遵循Java命名约定(下划线)
另外:
- 你几乎永远都不应该赶上
Exception
- 您应该关闭
finally
块中的资源
(我还没有对代码进行彻底的分析,这只是我的初步印象。)