datareader.java

一个Java持久层类库

package ActiveObject.core;

import ActiveObject.vo.TableType;
import ActiveObject.exception.*;
import java.sql.*;
import java.util.*;

/**
 *  @author tanjiazhang
 */
public class DataReader {

    private Connection connection = null;
    private PreparedStatement preparedStatement = null;
//    private Class objectType = null;
    List<TableType> tables = null;
    private ResultSet resultSet = null;


    DataReader (Connection connection, PreparedStatement pStmt, List<TableType> tables) throws java.sql.SQLException
    {
        this.connection = connection;//传入该参数是为了让它可在Reader内关闭
        this.preparedStatement = pStmt;
//        this.objectType = objectType;
        this.tables = tables;
        this.resultSet = pStmt.executeQuery();
    }

    private DataReader () {
    }

    /**
     * 尝试读一行记录，只有返回值为真时，才允许取出该对象
     * @throws java.sql.SQLException
     */
    public boolean read () throws java.sql.SQLException {
        return this.resultSet.next();
    }

    /**
     * 执行read()操作后，从DataReader中读出该对象
     * @throws java.sql.SQLException
     * @throws java.lang.IllegalAccessException 以下异常可能由于内部机制的实现问题而产生
     */
    public Object getObject () throws ObjectAnalysisException, SQLException{
        Object value = null;
        if(tables.size() > 1)
        {
            int tableCount = tables.size();
            Class[] objectTypes = new Class[tableCount];
            Map<String,String> tableName = new HashMap();
            for(int i=0;i<tableCount;i++)
            {
                TableType table = tables.get(i);
                objectTypes[i] = table.getObjectType();
                tableName.put(table.getObjectType().getSimpleName(), table.getNickName());
            }
            ActiveRecord[] objects = new ActiveRecord[tableCount];
            try
            {
                for(int j=0;j<tableCount;j++)
                    objects[j] = (ActiveRecord)objectTypes[j].newInstance();
            }
            catch(IllegalAccessException err)
            {
                throw new ObjectAnalysisException(err.toString(), err);
            }
            catch(InstantiationException err)
            {
                throw new ObjectAnalysisException(err.toString(), err);
            }
            value = ActiveRecordHelper.setupObjectByResultSet(objects, resultSet, tableName);
//            value = ActiveRecordHelper.setupObject(objects, tableName, this.resultSet);
        }
        else
        {
            Class<ActiveRecord> object = this.tables.get(0).getObjectType();
            try
            {
                value = ActiveRecordHelper.setupObjectByResultSet(object.newInstance(), resultSet);
//                value = ActiveRecordHelper.setupObject(object.newInstance(),this.resultSet);
            }
            catch(IllegalAccessException err)
            {
                throw new ObjectAnalysisException(err.toString(), err);
            }
            catch(InstantiationException err)
            {
                throw new ObjectAnalysisException(err.toString(), err);
            }
        }
        return value;
//        ActiveRecord record = null;
//        try
//        {
//            record = ActiveRecord.setupObject((ActiveRecord)objectType.newInstance(), this.resultSet);
//            record.isActive = true;
//        }
//        catch(ObjectAnalysisException err)
//        {
//            throw err;
//        }
//        catch(SQLException err)
//        {
//            throw err;
//        }
//        catch(Exception err)
//        {}
//        return record;
    }

    /**
     * 使用DataReader完毕后必须执行close释放资源
     * @throws java.sql.SQLException
     */
    public void close () throws java.sql.SQLException {
        this.resultSet.close();
        this.preparedStatement.close();
        this.connection.close();
    }
}