Collection 读数据库表读不了

[shgfzdw]

public Collection selTypeAll() {
Collection c = new ArrayList();
db_conn.ConnectDB();
ResultSet rs=null;
String sql = "select * from type";

try {

while (rs.next()) {
Type vo = new Type();
vo.setTypeid(rs.getInt(1));
vo.setTypename(rs.getString(2));

c.add(vo);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

return c;
}


连接没有错啊,为什么总是说空指针呢?
错误如下:
java.lang.NullPointerException
at zdw.db.DBType.selTypeAll(DBType.java:120)
at org.apache.jsp.admin.type.addgoodstype_jsp._jspService(addgoodstype_jsp.java:118)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)

[windy731]

ResultSet rs=null;
String sql = "select * from type";

try {

while (rs.next()) {


说的空应该是rs，没有进行查数据库的操作，就开始读rs了

[cjg520jie]

你应该先做数据库操作啊，没结果，怎么来的记录集

看下我写的代码

Connection conn = null;
PreparedStatement ps = null;
try{
Class.forName("oracle.jdbc.pool.OracleConnectionPoolDataSource").newInstance();
String url = "jdbc:oracle:thin:@192.168.0.166:1521:orcl";
String user = "km";
String password = "km";
conn= DriverManager.getConnection(url,user,password);
String sql = "SELECT * FORM ETIM0022";
ps = conn.prepareStatement(sql);
int i = ps.executeUpdate();
}catch(Exception e){
e.printStackTrace();
}finally{
try {
ps.close();
} catch (SQLException e) {
// TODO 自動生成された catch ブロック
e.printStackTrace();
}
try {
conn.close();
} catch (SQLException e) {
// TODO 自動生成された catch ブロック
e.printStackTrace();
}
}

你缺少红色的那段操作数据库