产品目录/论坛 树形结构的实现

答案：
本例采用Access做为实例，所有还有很多要改进的地方。 
请读者自已改进 
package product; 
import java.sql.*; 
public class ConnectDB{ 
String strDBDriver="sun.jdbc.odbc.JdbcOdbcDriver"; 
String strConnstr="jdbc:odbc:product"; 
Connection conn=null; 
ResultSet rs=null; 
Statement stmt=null; 
// Statement stmt=null; 
//构造函数 
public ConnectDB(){ 
try{ 
Class.forName(strDBDriver); conn=DriverManager.getConnection(strConnstr); 
stmt=conn.createStatement(); 
} 
catch(Exception e){ 
System.out.println(e); 
} 
} 
public ResultSet execute(String sql){ 
rs=null; 
try{ 
rs=stmt.executeQuery(sql); 
} 
catch(SQLException e){ 
System.out.println(e.getMessage()); 
} 
return rs; 
} 
public Connection getConnection(){ 
return conn; 
} 
public boolean close(){ 
try{ 
if(this.rs!=null){ 
this.rs.close(); 
} 
if(stmt!=null){ 
this.stmt.close(); 
} 
if(conn!=null){ 
this.conn.close(); 
} 
return true; 
}catch(Exception err){ 
return false; 
} 
} 
} 
//======================================= 
package product; 
import java.sql.*; 
public class catalog 
{ 
ConnectDB conn=new ConnectDB(); 
String str=null; 
String sql=null; 
ResultSet rs=null; 
String AncestorID,LinkStr; 
public String getCatalog(){ 
str="<select name=\"FatherID\" class=\"p9\">\n"+ 
"<option value=\"-1\" selected>请选择父类</option>\n"; 
String sql=null; 
sql="select * from catalog order by AncestorID,Linkstr"; 
ResultSet rs=conn.execute(sql); 
try{ 
while (rs.next()) { 
str=str+"<option value="+rs.getString("Productid")+">"; 
int nbspCount=rs.getString("LinkStr").length()-1; 
for(int i=0;i<nbspCount;i++){ 
str=str+" "; 
} 
if(nbspCount>0) 
str=str+"┠"+rs.getString("title")+"</option>\n"; 
else 
str=str+rs.getString("title")+"</option>\n"; 
} 
str=str+"</select>"; 
rs.close(); 
} 
catch(SQLException e){ 
System.out.println(e.getMessage()); 
} 
return str; 
} 
public void setCatalog(String CatalogName,String FatherID){ 
int ChildNum=0; 
if(FatherID.compareTo("-1")!=0){ 
sql="select AncestorID,ChildNum,linkstr from catalog where productid="+FatherID; 
//out.println(sql); 
try{ 
rs=conn.execute(sql); 
if(rs.next()){ 
AncestorID=rs.getString("AncestorID"); 
ChildNum=rs.getInt("ChildNum"); 
LinkStr=rs.getString("linkstr"); 
} 
else{ 
AncestorID=""; 
LinkStr="1"; 
ChildNum=0; 
} 
LinkStr=LinkStr+(ChildNum+1); 
//out.println(AncestorID+":"+LinkStr+":"+ChildNum); 
sql="insert into catalog(title,fatherID,AncestorID,LinkStr) values(''"+CatalogName+"'',''"+FatherID+"'',''"+AncestorID+"'',''"+LinkStr+"'')"; 
//out.println(sql); 
conn.execute(sql); 
sql="update catalog set childNum="+(ChildNum+1)+" where productID="+FatherID; 
//out.println("<br>"+sql); 
conn.execute(sql); 
}catch(Exception e){ 
System.out.println(e); 
} 
}else{ 
sql="insert into catalog(title,fatherID,LinkStr) values(''"+CatalogName+"'',''"+FatherID+"'',''1'')"; 
//out.println(sql); 
try{ 
conn.execute(sql); 
sql="select top 1 productID from catalog order by productID desc "; 
rs=conn.execute(sql); 
if(rs.next()){ 
AncestorID=rs.getString("productID"); 
} 
else{ 
AncestorID=""; 
} 
rs.close(); 
sql="update catalog set AncestorID=''"+AncestorID+"'' where productID="+AncestorID; 
//out.println(sql); 
conn.execute(sql); 
}catch(Exception e){ 
System.out.println(e); 
} 
}//end if 
if(rs!=null){ 
try{ 
rs.close(); 
}catch(Exception e){ 
System.out.println(e); 
} 
} 
} 
public void deleteCatalog(String FatherID){ 
int tempData=0; 
sql="select fatherID,linkstr,AncestorID from catalog where >rs=conn.execute(sql); 
try{ 
if(rs.next()){ 
tempData=rs.getInt("fatherID"); 
LinkStr=rs.getString("linkstr"); 
AncestorID=rs.getString("AncestorID"); 
} 
try{rs.close();} 
catch(Exception e){ 
System.out.println(e); 
} 
sql="delete from catalog where ProductID="+FatherID; 
// out.println(sql); 
try{ 
conn.execute(sql); 
}catch(Exception e){ 
System.out.println(e); 
} 
sql="delete from catalog where linkstr like ''"+LinkStr+"%'' and AncestorID="+AncestorID; 
//out.println(sql); 
try{ 
conn.execute(sql); 
}catch(Exception e){ 
System.out.println(e); 
} 
sql="update catalog set ChildNum=ChildNum-1 where productID="+tempData; 
//out.println(sql); 
try{ 
conn.execute(sql); 
}catch(Exception e){ 
System.out.println(e); 
} 
}catch(Exception e){ 
System.out.println(e); 
} 
} //end public 
public void updateCatalog(int id){ 
} 
public String getCatalog(int id){ 
str="<select name=\"FatherID\" class=\"p9\">\n"+ 
"<option value=\"-1\" >请选择父类</option>\n"; 
String sql=null; 
sql="select * from catalog order by AncestorID,Linkstr"; 
ResultSet rs=conn.execute(sql); 
try{ 
while (rs.next()) { 
int ProductID=rs.getInt("productID"); 
if (ProductID==id) { 
str=str+"<option value="+ProductID+" selected>"; 
} 
else{ 
str=str+"<option value="+ProductID+">"; 
} 
int nbspCount=rs.getString("LinkStr").length()-1; 
for(int i=0;i<nbspCount;i++){ 
str=str+" "; 
} 
if(nbspCount>0) 
str=str+"┠"+rs.getString("title")+"</option>\n"; 
else 
str=str+rs.getString("title")+"</option>\n"; 
} 
str=str+"</select>"; 
rs.close(); 
} 
catch(SQLException e){ 
System.out.println(e.getMessage()); 
} 
return str; 
} 
public String getCatalogList(){ 
str="<select name=\"FatherID\" class=\"p9\" size=\"20\" onClick=\"MM_jumpMenu(''parent.mainFrame'',this,0)\">\n"+ 
"<option value=\"-1\" selected>请选择父类</option>\n"; 
String sql=null; 
sql="select * from catalog order by AncestorID,Linkstr"; 
ResultSet rs=conn.execute(sql); 
try{ 
while (rs.next()) { 
str=str+"<option value="+rs.getString("Productid")+">"; 
int nbspCount=rs.getString("LinkStr").length()-1; 
for(int i=0;i<nbspCount;i++){ 
str=str+" "; 
} 
if(nbspCount>0) 
str=str+"┠"+rs.getString("title").trim()+"</option>\n"; 
else 
str=str+rs.getString("title")+"</option>\n"; 
} 
str=str+"</select>"; 
rs.close(); 
} 
catch(SQLException e){ 
System.out.println(e.getMessage()); 
} 
return str; 
} 
} 

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