一 点睛

在有些时候，单个线程执行的任务步骤会非常多，后一个步骤的输入可能是前一个步骤的输出，比如单个线程多步骤（阶段）执行时，为了使得功能单一，有时候我们会采用 GoF 职责链设计模式。

二 实战

1 线程上下文信息

package concurrent.context.improve;

/**
* 线程运行上下文设计模式
* 上下文
*
* @author cakin
*/
public class Context {
    private String name;
    private String cardId;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getCardId() {
        return cardId;
    }

    public void setCardId(String cardId) {
        this.cardId = cardId;
    }
}

2 从数据中查询数据

/**
* 线程运行上下文设计模式
* 从数据库查询数据
*
* @author cakin
*/
public class QueryFromDbAction {
    public void execute(Context context) {
        try {
            Thread.sleep(1000L);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        String name = "Alex-" + Thread.currentThread().getName();
        context.setName(name);
    }
}

3 从接口中获取数据

package concurrent.context;

/**
* 线程运行上下文设计模式
* 调用接口获取数据
*
* @author cakin
*/
public class QueryFromHttpAction {
    public void execute(Context context) {
        try {
            Thread.sleep(1000L);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        String name = context.getName();
        String cardId = getCardId(name);
        context.setCardId(cardId);
    }

    private String getCardId(String name) {
        try {
            Thread.sleep(1000L);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "510823" + Thread.currentThread().getId();
    }
}

4 线程执行任务

package concurrent.context;

/**
* 线程运行上下文设计模式
* 线程执行任务
*
* @author cakin
*/
public class ExecutionTask implements Runnable {
    private QueryFromDbAction queryAction = new QueryFromDbAction();
    private QueryFromHttpAction httpAction = new QueryFromHttpAction();

    @Override
    public void run() {
        Context context = new Context();
        queryAction.execute(context);
        System.out.println("The name query successful.");
        httpAction.execute(context);
        System.out.println("The card id query successful.");
        System.out.println("The Name is " + context.getName() + " and CardId is " + context.getCardId());
        System.out.println(context);
    }
}

5 测试

package concurrent.context;

import java.util.stream.IntStream;

/**
* 线程运行上下文设计模式
* 上下文测试
*
* @author cakin
*/
public class ContextTest {
    public static void main(String[] args) {
        IntStream.rangeClosed(1, 4).forEach(i -> {
            new Thread(new ExecutionTask(), "T" + i).start();
        });
    }
}

三 测试结果

The name query successful.

The name query successful.

The name query successful.

The name query successful.

The card id query successful.

The card id query successful.

The Name is Alex-T2 and CardId is 51082313

The card id query successful.

The Name is Alex-T4 and CardId is 51082315

concurrent.context.Context@244c2a61

The card id query successful.

The Name is Alex-T3 and CardId is 51082314

concurrent.context.Context@1a712b8a

The Name is Alex-T1 and CardId is 51082312

concurrent.context.Context@7d67eaea

concurrent.context.Context@237cd6cd