写的一个分类显示

package cn.dao;

import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;

import cn.itcast.domain.Category;
import cn.itcast.utils.JdbcUtils;

public class CategoryDao {

public List<Category> getAll(){

try{
QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());
String sql = "select child.id,child.name,count(child.name) depth from category parent,category child where parent.lft<=child.lft and parent.rgt>=child.rgt group by child.name order by child.lft";

List list = (List) runner.query(sql, new BeanListHandler(Category.class));
return list;
}catch (Exception e) {
throw new RuntimeException(e);
}
}

public Category find(String id) {
try{
QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());
String sql = "select * from category where id=?";
Category c = (Category) runner.query(sql, id, new BeanHandler(Category.class));

sql = "select * from category where lft<? and rgt>? order by lft";
Object params[] = {c.getLft(),c.getRgt()};
List list = (List) runner.query(sql, params, new BeanListHandler(Category.class));
c.setParents(list);
return c;
}catch (Exception e) {
throw new RuntimeException(e);
}
}

public void insertUpdate(int rgt) { //7
try{
QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());
String sql1 = "update category set lft=lft+2 where lft>=?";
String sql2 = "update category set rgt=rgt+2 where rgt>=?";

runner.update(sql1, rgt);
runner.update(sql2, rgt);
}catch (Exception e) {
throw new RuntimeException(e);
}

}

public void add(Category child) {

try{
QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());
String sql = "insert into category(id,name,lft,rgt) values(?,?,?,?)";
Object params[] = {child.getId(),child.getName(),child.getLft(),child.getRgt()};
runner.update(sql, params);
}catch (Exception e) {
throw new RuntimeException(e);
}


}

}