深入Java设计模式之策略模式

package com.lzhsite.technology.designPattern.strategy.LogTemplateDemo;
public class ClientForLogTemplateDemo
{
    public static void main(String[] args)
    {
        LogContext logContext = new LogContext();
        logContext.log("记录日志");
        logContext.log("再次记录日志");
    }
}

package com.lzhsite.technology.designPattern.strategy.LogTemplateDemo;
public class DBLog extends LogStrategyTemplate {
  protected void doLog(String logMessage) {
    if (logMessage != null && logMessage.trim().length() > 5) {
      int a = 5 / 0;
    }
    System.out.println("现在把 '" + logMessage + "' 记录到数据库中");
  }
}

package com.lzhsite.technology.designPattern.strategy.LogTemplateDemo;
public class FileLog extends LogStrategyTemplate
{
    protected void doLog(String logMessage)
    {
        System.out.println("现在把 '" + logMessage + "' 记录到文件中");
    }
}

package com.lzhsite.technology.designPattern.strategy.LogTemplateDemo;
public class LogContext {
  public void log(String logMessage) {
    LogStrategy strategy = new DBLog();
    try {
      //这里进行了策略的选择吧try-catch变相当if else用了
      strategy.log(logMessage);
    } catch (Exception exception) {
      strategy = new FileLog();
      strategy.log(logMessage);
    }
  }
}

package com.lzhsite.technology.designPattern.strategy.LogTemplateDemo;
public interface LogStrategy
{
    public void log(String logMessage);
}

package com.lzhsite.technology.designPattern.strategy.LogTemplateDemo;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
public abstract class LogStrategyTemplate implements LogStrategy
{
    public final void log(String logMessage)
    {
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss SSS");
        logMessage = dateFormat.format(new Date()) + " 内容是：" + logMessage;
        doLog(logMessage);
    }
    protected abstract void doLog(String logMessage);
}