关于DAO访问数据库的问题~）

Question

将rs.next()循环出来的数据在放到set里面去不就可以了，但是set中不能有重复元素！

Answer 1

从ResultSet里一个一个取出来，利用各字段构造成一个所需的对象，塞到Set里去。

Answer 2

贴一段你看看：
Connection conn = null;
try {
System.out
.println("DVBAppInfoFacadeDAOImpl#findAppInfoListByServiceRef serviceRef : "
+ serviceRef);
conn = ds.getConnection();
PreparedStatement ps;
Collection c = new ArrayList();
String query = "SELECT"
+ " A.id,A.component_tag,A.service_ref,P.id,A.application_type,"
+ " A.descriptor_tag0x52,A.descriptor_data0x52,A.descriptor_tag0x6f,"
+ " A.descriptor_data0x6f,A.rate"
+ " FROM dvb_ait_stream AS A,dvb_pid AS P"
+ " WHERE A.service_ref=?" + " AND A.pid_ref=P.id";
ps = conn.prepareStatement(query);
ps.setInt(1, serviceRef);
ResultSet rs = ps.executeQuery();
while (rs.next()) {
DVBAppInfoData daid = new DVBAppInfoData();
daid.setId(new Integer(rs.getInt("id")));
daid.setComponentTag(new Integer(rs.getInt(2)));
daid.setServiceRef(new Integer(rs.getInt(3)));
daid.setPidRef(new Integer(rs.getInt(4)));
daid.setApplicationType(new Integer(rs.getInt(5)).toString());
daid.setDescriptorTag0x52(rs.getBytes("descriptor_tag0x52"));
daid.setDescriptorData0x52(rs.getBytes("descriptor_data0x52"));
daid.setDescriptorTag0x6f(rs.getBytes("descriptor_tag0x6f"));
daid.setDescriptorData0x6f(rs.getBytes("descriptor_data0x6f"));
daid.setRate(new Integer(rs.getInt("rate"))); c.add(daid); }
rs.close();
ps.close();
return c;
....

Answer 3

ResultSet rs = sql.executeQuery();
while (rs.next()){....};