Apache commons-chain

在日常的工作中，我们经常会碰到一些业务流程比较复杂的场景，这些东西糅合到一个方法里就使得代码耦合度特别高，随着业务场景逻辑的越来越多，就会越来越复杂，难以维护。
如提交的订单的动作可能涉及到如下场景：

1. 各种各样的校验
2. 各类信息的补充
3. 订单提交成功/失败后产品信息/库存的改变
4. 订单提交成功/失败后支付信息/状态的改变
5. 订单提交成功/失败后的各种推送
6. 等等

还有一些更复杂的场景是要根据类型区分的，如不同的产品类型后续执行的动作是不一样的，假设某一类产品是不需要推送的，可能第5步就不需要

项目中用过这么一个东西，Apache commons chain，原理是责任链模式。大致实现方式是根据不同的业务场景，建立多个Command，每个Command处理各自的业务逻辑，每个Command执行完毕后，将处理后的处理传给下一个Command，直到所有执行完毕。

接口原理图

代码实现

1. 建立ChainBase，可以根据不同的应用场景建立多个ChainBase，如下示例我使用了1、2、3三个Command，当然我也可以根据需要只使用1和2

package com.mk.chain;

import com.mk.chain.commands.Commands1;
import com.mk.chain.commands.Commands2;
import com.mk.chain.commands.Commands3;
import org.apache.commons.chain.Command;
import org.apache.commons.chain.impl.ChainBase;

public class CommandChain extends ChainBase{
    public CommandChain() {
        addCommand(new Commands1());
        addCommand(new Commands2());
        addCommand(new Commands3());
    }
}

2. 建立对应的Command，每个Command都是一个独立的类，需要实现Command接口

Commands1.java

package com.mk.chain.commands;

import com.alibaba.fastjson.JSONObject;
import io.swagger.models.auth.In;
import org.apache.commons.chain.Command;
import org.apache.commons.chain.Context;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Commands1 implements Command{

    private static final Logger logger = LoggerFactory.getLogger(Commands1.class);


    @Override
    public boolean execute(Context context) throws Exception {
        Object v1 = context.get("k1");
        logger.info("do something by Commands1... params is {}", JSONObject.toJSONString(context));
        if(v1 != null){
            int IntV1 = (Integer) v1;
            context.put("k1", IntV1+1);
        }
        return false;
    }
}

Commands2.java

package com.mk.chain.commands;

import com.alibaba.fastjson.JSONObject;
import org.apache.commons.chain.Command;
import org.apache.commons.chain.Context;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Commands2 implements Command{

    private static final Logger logger = LoggerFactory.getLogger(Commands2.class);


    @Override
    public boolean execute(Context context) throws Exception {
        Object v1 = context.get("k1");
        logger.info("do something by Commands2... params is {}", JSONObject.toJSONString(context));
        if(v1 != null){
            int IntV1 = (Integer) v1;
            context.put("k1", IntV1+1);
        }
        return false;
    }
}

Commands3.java

package com.mk.chain.commands;

import com.alibaba.fastjson.JSONObject;
import org.apache.commons.chain.Command;
import org.apache.commons.chain.Context;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Commands3 implements Command{

    private static final Logger logger = LoggerFactory.getLogger(Commands3.class);


    @Override
    public boolean execute(Context context) throws Exception {
        Object v1 = context.get("k1");
        logger.info("do something by Commands3... params is {}", JSONObject.toJSONString(context));
        if(v1 != null){
            int IntV1 = (Integer) v1;
            context.put("k1", IntV1+1);
        }
        return false;
    }
}

3. 测试，建立测试类CommandTest.java

package com.my.test;

import com.mk.chain.CommandChain;
import org.apache.commons.chain.Context;
import org.apache.commons.chain.impl.ContextBase;
import org.junit.Test;

public class CommandTest {

    @Test
    public void test() throws Exception {
        CommandChain commandChain = new CommandChain();
        Context context = new ContextBase();
        context.put("k1",1);
        commandChain.execute(context);
    }
}

执行结果如下

2018-01-19 10:20:54.356 [main] INFO  com.mk.chain.commands.Commands1 - do something by Commands1... params is {"k1":1}
2018-01-19 10:20:54.363 [main] INFO  com.mk.chain.commands.Commands2 - do something by Commands2... params is {"k1":2}
2018-01-19 10:20:54.363 [main] INFO  com.mk.chain.commands.Commands3 - do something by Commands3... params is {"k1":3}