ModelBuilder.java

package li.dao;

import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import li.model.Field;
import li.util.Log;
import li.util.Reflect;

/**
 * Dao辅助类,从ResultSet中读取数据并组装对象
 * 
 * @author li (limingwei@mail.com)
 * @version 0.1.5 (2012-05-08)
 * @see li.util.Reflect
 */
public class ModelBuilder {
    private static final Log log = Log.init();

    /**
     * 保存当前查询的QueryRunner,为了回调以关闭Connection
     */
    protected QueryRunner queryRunner;

    /**
     * 当前ModelBuilder的结果集
     */
    protected ResultSet resultSet;

    /**
     * 初始化一个ModelBuilder
     */
    public ModelBuilder(QueryRunner queryRunner, ResultSet resultSet) {
        this.queryRunner = queryRunner;
        this.resultSet = resultSet;
    }

    /**
     * 从ResultSet中提取数据组装成type类型的对象的 List
     * 
     * @param type 对象类型
     * @param fields 对象属性列表
     * @param count 组装对象最大个数
     * @param close 是否于读取后关闭resultSet
     */
    public <T> List<T> list(Class<T> type, List<Field> fields, Integer count, Boolean close) {
        List<T> list = new ArrayList<T>();
        try {
            while (null != resultSet && resultSet.next() && (null == count || list.size() <= count)) {
                T t = Reflect.born(type);
                for (Field attribute : fields) {
                    Reflect.set(t, attribute.name, value(attribute.column, false, false));
                }
                list.add(t);
            }
            log.trace("build ? ?", list.size(), type.getName());
        } catch (Exception e) {
            throw new RuntimeException(e + " ", e);
        } finally {
            if (close) {
                this.close();
            }
        }
        return list;
    }

    /**
     * 辅助方法,封装后的resultSet.getString(column);
     * 
     * @param column 数据所在的列名或者顺序,String或者Integer类型
     * @param next 读取前是否 resultSet.next()
     * @param close 是否于读取后关闭resultSet
     */
    public String value(Object column, Boolean next, Boolean close) {
        try {
            if ((null != resultSet) && ((next && resultSet.next()) || !next)) { // 若next==true,则resultSet.next()
                if (column instanceof String) {// 按列名查找
                    return resultSet.getString((String) column);
                } else if (column instanceof Integer) {// 按index查找
                    return resultSet.getString((Integer) column);
                } else {
                    throw new RuntimeException("column must be String or Integer");
                }
            }
        } catch (Exception e) {
            throw new RuntimeException(e + " ", e);
        } finally {
            if (close) {
                this.close();
            }
        }
        return null;
    }

    /**
     * 关闭ModelBuilder,关闭ResultSet,PreparedStatement和Connection
     * 
     * @see li.dao.QueryRunner#close()
     */
    protected void close() {
        try {
            if (null != resultSet) {
                resultSet.close();// 关闭ResultSet
                log.trace("Closed ResultSet ?", resultSet);
            }
            if (null != queryRunner) {
                queryRunner.close();// 关闭QueryRunner,他会关闭PreparedStatement和Connection
                log.trace("Closed QueryRunner ?", queryRunner);
            }
        } catch (Exception e) {
            throw new RuntimeException(e + " ", e);
        }
    }
}