Apache Commons Chain(2) -开源责任链模式（apache commons chain）

前一篇文章，我们大概介绍了 Apache commons chain 及完成了一个简单的demo ,今天我们就从源码级别来分析下，到底是一个什么样的执行流程 ~~~~！

首先从执行入口类：

public class CommondChain extends ChainBase {

    public CommondChain() {
        super();
        addCommand(new GetUserInfo());
        addCommand(new TestDriver());
        addCommand(new NegotiateSale());
        addCommand(new ArrangeFinancing());
        addCommand(new CloseSale());
    }

    public static void main(String[] args) {
        CommondChain commondChain = new CommondChain();
        Context context = new ContextBase();

        try {
            commondChain.execute(context);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

我们从两个方面来进行源码解析：

1、实现了Command 的业务功能如何加入容器中？加入到什么容器中？

具体实现在 ChainBase.class

   public void addCommand(Command command) {

        if (command == null) {
            throw new IllegalArgumentException();
        }
        if (frozen) {
            throw new IllegalStateException();
        }
        Command[] results = new Command[commands.length + 1];
        System.arraycopy(commands, 0, results, 0, commands.length);
        results[commands.length] = command;
        commands = results;

    }

其中，commands 为数组类型。说白了就是加入一个业务处理command 就追加到数组里面去。

如何执行这个流程呢？

具体调用也是在 ChainBase.class

  public boolean execute(Context context) throws Exception {

        // Verify our parameters
        if (context == null) {
            throw new IllegalArgumentException();
        }

        // Freeze the configuration of the command list
        frozen = true;

        // Execute the commands in this list until one returns true
        // or throws an exception
        boolean saveResult = false;
        Exception saveException = null;
        int i = 0;
        int n = commands.length;
        for (i = 0; i < n; i++) {
            try {
                saveResult = commands[i].execute(context);
                if (saveResult) {
                    break;
                }
            } catch (Exception e) {
                saveException = e;
                break;
            }
        }

        // Call postprocess methods on Filters in reverse order
        if (i >= n) { // Fell off the end of the chain
            i--;
        }
        boolean handled = false;
        boolean result = false;
        for (int j = i; j >= 0; j--) {
            if (commands[j] instanceof Filter) {
                try {
                    result =
                        ((Filter) commands[j]).postprocess(context,
                                                           saveException);
                    if (result) {
                        handled = true;
                    }
                } catch (Exception e) {
                      // Silently ignore
                }
            }
        }

        // Return the exception or result state from the last execute()
        if ((saveException != null) && !handled) {
            throw saveException;
        } else {
            return (saveResult);
        }

    }

看下代码实现思路还是很简单的哈~~