是用JDBC从数据库中获取数据并以java对象返回

/**
*
* @param c
*            for example Person.class
* @param primaryKeys
*            primaryKeys为主键,参数顺序和表中保持一致 如果id， name 为主键 类名为Person 则 getEntity(Person.class,1,"name")
* @return
*/
public static Object getEntity(Class c, Object... primaryKeys) {
PreparedStatement ps = null;
ResultSet rs = null;
DatabaseMetaData dmd = null;
Object obj = null;// 要返回的对象
String tableName = c.getSimpleName().toLowerCase();// person 表的名字
List primaryKeyNameList = new ArrayList();
Field[] fields = c.getFields();// 获取所有的属性
StringBuilder sql = new StringBuilder("select * from " + tableName
+ " where ");
try {
obj = c.newInstance();
dmd = getConnection().getMetaData();
rs = dmd.getPrimaryKeys(null, null, tableName);
while (rs.next()) {
sql.append(rs.getObject(4) + "=?");
sql.append(" and ");
primaryKeyNameList.add(rs.getObject(4));// 将从表中获取的 主键字段存到 list中， 主键位于表中第几列=rs.getString(5)
}
sql.delete(sql.length() - 4, sql.length());
ps = (PreparedStatement) getConnection().prepareStatement(
sql.toString());
for (int l = 0; l < primaryKeyNameList.size(); l++) {
ps.setObject(l + 1, primaryKeys[l]);
}
rs = ps.executeQuery();
System.out.println(ps.toString().split(":")[1]);
if (rs.next()) {
for (int k = 0; k < fields.length; k++) {
fields[k].set(obj, rs.getObject(k + 1));
}
}
rs.close();
ps.close();
rs=null;
ps=null;
} catch (Exception e) {
e.printStackTrace();
} finally {

}
return obj;
}