模拟域对象" class="reference-link">10.6 模拟域对象

遇到了另一个常见的问题,同时为Spring Batch编写单元测试和集成测试组件是如何模拟域对象。一个很好的例子是StepExecutionListener,如下所示:

  1. public class NoWorkFoundStepExecutionListener extends StepExecutionListenerSupport {
  3.     public ExitStatus afterStep(StepExecution stepExecution) {
  4.         if (stepExecution.getReadCount() == 0) {
  5.             throw new NoWorkFoundException("Step has not processed any items");
  6.         }
  7.         return stepExecution.getExitStatus();
  8.     }
  9. }

上面的监听是框架提供的，并且它检测到stepExecution的read count是为空的，因此它表示没有工作要做。虽然这个例子相当简单，当试图单元测试类的时候它解释了可能遇到的问题类型,实现接口验证Spring Batch 域对象。考虑到上面的侦听器的单元测试:

  1. private NoWorkFoundStepExecutionListener tested = new NoWorkFoundStepExecutionListener();
  3. @Test
  4. public void testAfterStep() {
  5.     StepExecution stepExecution = new StepExecution("NoProcessingStep",
  6.                 new JobExecution(new JobInstance(1L, new JobParameters(),
  7.                                  "NoProcessingJob")));
  9.     stepExecution.setReadCount(0);
  11.     try {
  12.         tested.afterStep(stepExecution);
  13.         fail();
  14.     } catch (NoWorkFoundException e) {
  15.         assertEquals("Step has not processed any items", e.getMessage());
  16.     }
  17. }

因为Spring Batch域模型遵循良好的面向对象原则，StepExecution需要一个JobExecution，JobExecution需要一个JobInstance和JobParameters为了创建一个有效的StepExecution。虽然这是很好的可靠的域模型,为了冗长的单元测试创建存根对象。为了解决这个问题，Spring Batch测试模块引入一个工厂来创建域对象:MetaDataInstanceFactory，把这个给到工厂，更新后的单元测试可以更简洁：

  1. private NoWorkFoundStepExecutionListener tested = new NoWorkFoundStepExecutionListener();
  3. @Test
  4. public void testAfterStep() {
  5.     StepExecution stepExecution = MetaDataInstanceFactory.createStepExecution();
  7.     stepExecution.setReadCount(0);
  9.     try {
  10.         tested.afterStep(stepExecution);
  11.         fail();
  12.     } catch (NoWorkFoundException e) {
  13.         assertEquals("Step has not processed any items", e.getMessage());
  14.     }
  15. }

上面的方法为了创建一个简单的StepExecution，它仅仅是便利的方法中可用的工厂。完整的方法清单可以在Javadoc找到