模板模式应用一例

CTO给的设计是这样的：一个管理类DataLoaderManager，一个接口DataLoader，n个DataLoader实现。

我添加了一个对DataLoader的抽象类AbstractDataLoader，抽出实现中普遍用到的方法。

java 代码

public interface DataLoader {
    /**
     * load data
     * @param dataMessage
     * @return true - if successful
     * @throws DataLoadException
     * @see
     */
    public boolean loadData(VoDataLoad dataload) throws DataLoadException;

}

 

java 代码

public abstract class AbstractDataLoader {
    public void lockDataLoad(VoDataLoad dataload) throws DataLoadException {
        // implement code
    }

    public void processErrorDataLoad VoDataLoad dataload) throws DataLoadException {
        // implement code
        sendEmailToAdmin(dataload);
    }

    public void sendEmailToAdmin(VoDataLoad dataload) {
        // implement code
    }
}

一个实现：

java 代码

public class FxRateLoader extends AbstractDataLoader implements DataLoader {

    public boolean loadData(VoDataLoad dataload) throws DataLoadException {
        try {
            // call getFxRateListget() to get a Vo array
        } catch (Exception e) {
           // process exception
        }
        // process other biz
    }

    private VoFXRate[] getFxRateList(VoDataLoad dataload) throws Exception {
        // code
    }
}

另外个接口实现

java 代码

public class GlobalIndexLoader extends AbstractDataLoader implements DataLoader {
    public boolean loadData(VoDataLoad dataload) throws DataLoadException {
        try {
            // call getIndexList() to get a Vo array
        } catch (Exception e) {
            // process exception
        }

        // process other biz
    }

    private VoIntIndex[] getIndexList(VoDataLoad dataload) throws Exception {
        // code
    }
}

不难发现，他们的流程几乎完全一致，可以用模板模式改造一下：

首先改造他们的抽象类AbstractDataLoader，把它的子类的实现流程拿上来，构造流程中的抽象方法，让子类实现。这样的话，第三个，第四个实现就无需重复很多代码了。

java 代码

public abstract class AbstractDataLoader implements DataLoader {
    private static Logger logger = Logger.getInstance(DataLoaderManager.class.getName());
    /**
     * load data, subclass must implement all abstract method
     * @param dataload
     * @return true if ok, else false.
     * @throws DataLoadException
     */
    public boolean loadData(VoDataLoad dataload) throws DataLoadException {
        if (dataload == null) throw new IllegalArgumentException();

        Object[] voList = null;
        try {
            this.getVoList(dataload);
        } catch (Exception e) {
            this.processException(dataload, e);
        }

        if (voList != null) {
            return this.processVoList(dataload, voList);
        } else {
            return false;
        }
    }
    /**
     * lock dataload if can not update now
     * @param dataload
     * @throws DataLoadException
     */
    public void lockDataLoad(VoDataLoad dataload) throws DataLoadException {
        DataLoadBo bo = new DataLoadBo();
        dataload.setDataStatus(CdaConstants.LOCKED);
        try {
            bo.updateStatus(dataload);
        } catch (AppSystemException e1) {
            logger.error("error", e1);
            throw new DataLoadException(e1.getMessage());
        }
    }
    /**
     * if something wrong, we set dataload status to be E, which means error.
     * @param dataload
     * @throws DataLoadException
     */
    protected void processErrorDataLoad(VoDataLoad dataload) throws DataLoadException {
        DataLoadBo bo = new DataLoadBo();
        dataload.setDataStatus(CdaConstants.ERROR);
        try {
            bo.updateStatus(dataload);
        } catch (AppSystemException e) {
            throw new DataLoadException(e.getMessage());
        }

        sendEmailToAdmin(dataload);
    }
    /**
     * get array of VO, such as VoIntIndex, VoFXRate
     * @param dataload
     * @return
     * @throws DataLoadException
     */
    protected abstract Object[] getVoList(VoDataLoad dataload) throws DataLoadException;
    /**
     * Everything is OK, we process Vo array
     * @param dataload
     * @param voList
     * @return
     * @throws DataLoadException
     */
    protected abstract boolean processVoList(VoDataLoad dataload, Object[] voList) throws DataLoadException;
    /**
     * If something is wrong, before set dataload to be Error,
     * we should try to extract error message and process this exception
     * @param dataload
     * @param e
     * @throws DataLoadException
     */
    protected abstract void processException(VoDataLoad dataload, Exception e) throws DataLoadException;
    /**
     * send email to notify administrator
     * @param dataload
     * @throws DataLoadException
     */
    public void sendEmailToAdmin(VoDataLoad dataload) throws DataLoadException{
        // TODO waiting for Jiang's assign
    }
}

改造第一个接口实现为：

java 代码

public class FxRateLoader extends AbstractDataLoader implements DataLoader {

    protected Object[] getVoList(VoDataLoad dataload) throws DataLoadException {
        // code
    }

    protected void processException(VoDataLoad dataload, Exception e) throws DataLoadException {
        // code
    }

    protected boolean processVoList(VoDataLoad dataload, Object[] fxRateList) throws DataLoadException {
        // code
    }
}

哈哈，打完收工。 测试一把，通过，ok！