java junit测试错误ClassCastException

Question

在尝试运行junit测试时，我遇到以下错误-

java.lang.ClassCastException: business.Factory cannot be cast to services.itemservice.IItemsService
at business.ItemManager.get(ItemManager.java:56)
at business.ItemMgrTest.testGet(ItemMgrTest.java:49)

导致问题的具体测试是

@Test
public void testGet() {
        Assert.assertTrue(itemmgr.get(items));
}

它正在测试的代码是

public boolean get(Items item)  { 

        boolean gotItems = false;       

        Factory factory = Factory.getInstance();

        @SuppressWarnings("static-access")
        IItemsService getItem = (IItemsService)factory.getInstance();

        try {
            getItem.getItems("pens", 15, "red", "gel");
            gotItems = true;
        } catch (ItemNotFoundException e) {
            // catch
            e.printStackTrace();
            System.out.println("Error - Item Not Found");
        }
        return gotItems;
    }

存储项目的测试几乎是一样的，效果很好

工厂班是

public class Factory {

    private Factory() {}
    private static Factory Factory = new Factory();
    public static Factory getInstance() {return Factory;}




    public static IService getService(String serviceName) throws ServiceLoadException {
        try {
            Class<?> c = Class.forName(getImplName(serviceName));
            return (IService)c.newInstance();
        } catch (Exception e) {
            throw new ServiceLoadException(serviceName + "not loaded");
        }
    }



    private static String getImplName (String serviceName) throws Exception {
        java.util.Properties props = new java.util.Properties();
            java.io.FileInputStream fis = new java.io.FileInputStream("config\\application.properties");
                props.load(fis);
                    fis.close();
                    return props.getProperty(serviceName);
}
}

Answer 1

你的工厂。getInstance方法返回一个Factory对象，而Factory不是IItemsService。也许你需要改变以下几点：

@SuppressWarnings("static-access")
IItemsService getItem = (IItemsService)factory.getInstance();

致：

@SuppressWarnings("static-access")
IItemsService getItem = (IItemsService)factory.getService(serviceName);

Answer 2

你调用了错误的方法。方法Factory.getInstance()返回一个实例（根据您的实现，它是单例的），因此当您将Factory强制转换为IItemService时，它将抛出一个ClassCastException

我在Factory中没有看到任何返回IItemService的方法。这里唯一有意义的方法是getService，它返回一个IService。但是，如果您尝试将IService强制转换为IItemService，它可能会抛出ClassCastException，并且IItemService不会扩展iSeries