JAVA高级面试进阶训练营视频教程

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一、先说一个结论：单元测试与主项目的spring容器是隔离的，也就是说，单元测试无法访问主项目spring容器，需要自己加载spring容器。

接下来是代码实例，WEB主项目出于运行状态，单元测试中可能会看到如下这样的代码：

代码一：当前类加载式

public class TestSpring { @Test public void testSpring(){ LoginService loginService = this.getBean("loginService"); } //以下为容器实例声明及初始化、销毁 private ClassPathXmlApplicationContext context; @Before public void before(){ //加载spring容器 context = new ClassPathXmlApplicationContext("spring-context.xml"); } @After public void after(){ context.destroy(); } //从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型. public <T> T getBean(String name) { return (T) context.getBean(name); } //从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型. public <T> T getBean(Class<T> requiredType) { return context.getBean(requiredType); } }

代码二：继承加载式

/** * @Description: 登录单元测试类 */ public class LoginTest extends SpringJunitSupport{ @Autowired private LoginService loginService; @Test public void testLogin(){ loginService.login(); } 

//让单元测试运行于spring环境，保证拥有spring框架相关支持 @RunWith(SpringJUnit4ClassRunner.class) //加载spring容器 @ContextConfiguration("classpath:/spring-context.xml") public class SpringJunitSupport { }

 

代码三：动态添加spring配置文件式

/** * @Description: 登录单元测试类 */ public class LoginTest{ //使用@Before注解方式加载spring容器配置文件，就不能通过自动装配的方式注入bean，因为自动装配注解执行要早于@Before //@Autowired private LoginService loginService; private TestSpringContextSupport springContextSupport = null; @Before public void setUp() throws Exception { springContextSupport = new TestSpringContextSupport(); //初始化spring容器时，再动态添加spring bean配置文件 springContextSupport.init(new String[] { "classpath:/support-quartz.xml" }); loginService = springContextSupport.getBean("loginService"); } @Test public void testLogin(){ loginService.login(); } }

public class TestSpringContextSupport { //通过静态语句块初始化一个静态变量，用于存放spring容器配置文件 public static List<String> contextList = new ArrayList<String>(); static { contextList.add("classpath:/spring-context.xml"); } private ApplicationContext context; //定义初始化方法，动态添加spring配置文件到静态配置文件集合 public void init(String[] contextFile) { List<String> list = new ArrayList<String>(); list.addAll(contextList); for (int i = 0; contextFile != null && i < contextFile.length; i++) { list.add(contextFile); } String[] x = new String[list.size()]; list.toArray(x); //加载spring容器 context = new ClassPathXmlApplicationContext(x); } //从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型. public <T> T getBean(String name) { return (T) context.getBean(name); } //从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型. public <T> T getBean(Class<T> requiredType) { return context.getBean(requiredType); } }

 

如上面三种方式，有一个共同点，就是在单元测试方法执行前，都大费周章的去加载了spring容器。 
web主项目出于运行状态，单元测试为什么还要单独加载spring容器，因为web主项目的spring容器对单元测试是隔离的，通过如下手段验证：

验证1：

把单元测试所有加载spring容器的代码去掉，保证主项目出于运行状态，通过@Autowired注解(@Autowired注解可以装配spring内部bean)，获取spring应用上下文的bean，然后再通过其获取业务bean，代码如下：

/** * @Description: 登录单元测试类 */ public class LoginTest{ //自动装配spring应用上下文bean @Autowired private ApplicationContext context; @Test public void testLogin(){ //通过应用上下文bean，获取业务bean LoginService loginService = (LoginService)context.getBean("loginService"); loginService.login(); } }

结果一定是空指针异常，context对象为null。

验证二，把web主项目停掉，单元测试使用上面第二种继承的方式加载spring容器，其它同上，代码如下：

/** * @Description: 登录单元测试类，继承SpringJunitSupport加载spring容器 */ public class LoginTest extends SpringJunitSupport{ //自动装配spring应用上下文bean @Autowired private ApplicationContext context; @Test public void testLogin(){ //通过应用上下文bean，获取业务bean LoginService loginService = (LoginService)context.getBean("loginService"); loginService.login(); } }

@RunWith(SpringJUnit4ClassRunner.class) //加载spring容器 @ContextConfiguration("classpath:/spring-context.xml") public class SpringJunitSupport { }

结果一切正常，如此就验证了单元测试与主项目的spring容器是隔离的，单元测试必须自己加载spring容器。 

上面一直在说加载spring容器，其实就是加载配置文件，把配置文件里面的bean加载到spring容器中，上面的验证也一直通过在spring容器中搜索bean对象进行的，理解并应用这一点是非常重要的。 

最后的彩蛋，理解是因为项目中有困惑，探究之后才能领悟透彻，比如一个实例：

1、主项目运行，提供服务接口，采用的方式为dubbo+zookeeper方式；

2、单元测试，调用提供者提供的服务，采用继承式加载spring配置文件；

3、抛出异常：地址已经被绑定使用(Address already in use: bind)

java.lang.IllegalStateException: Failed to load ApplicationContext ...... Caused by: com.alibaba.dubbo.rpc.RpcException: Fail to start server(url: dubbo://127.0.0.1:20880/...... ...... Caused by: com.alibaba.dubbo.remoting.RemotingException: Failed to bind NettyServer on /127.0.0.1:20880, cause: Failed to bind to: /0.0.0.0:20880 ...... Caused by: org.jboss.netty.channel.ChannelException: Failed to bind to: /0.0.0.0:20880 ...... Caused by: java.net.BindException: Address already in use: bind ......

4、异常原因：因为采用的是dubbo+zookeeper方式，主项目spring提供者注册了127.0.0.1:20880，单元测试加载spring配置文件想要注册0.0.0.0:20880地址，但是20880已经被主容器占用，所以单元测试无法正常加载。

5、解决办法：将主容器停掉，单独使用单元测试，即作为服务端又作为客户端

6、再次抛出异常：

DEBUG [2016-08-18 18:30:26,603] - ZkClient.java () - Closing ZkClient... INFO [2016-08-18 18:30:26,603] - ZkEventThread.java () - Terminate ZkClient event thread. DEBUG [2016-08-18 18:30:26,603] - ZkConnection.java () - Closing ZooKeeper connected to 119.254.166.167:2181 DEBUG [2016-08-18 18:30:26,603] - ZooKeeper.java () - Closing session: 0x15678a538f900ef DEBUG [2016-08-18 18:30:26,603] - ClientCnxn.java () - Closing client for session: 0x15678a538f900ef ...... DEBUG [2016-08-18 18:30:26,808] - ZkClient.java () - Closing ZkClient...done INFO [2016-08-18 18:30:26,810] - DubboProtocol.java () - [DUBBO] Close dubbo server: /127.0.0.1:20880, dubbo version: 2.5.4, current host: 127.0.0.1 INFO [2016-08-18 18:30:26,812] - AbstractServer.java () - [DUBBO] Close NettyServer bind /0.0.0.0:20880, export /127.0.0.1:20880, dubbo version: 2.5.4, current host: 127.0.0.1 INFO [2016-08-18 18:30:26,812] - ClientCnxn.java () - EventThread shut down for session: 0x15678a538f900ef ERROR [2016-08-18 18:30:26,813] - FailbackRegistry.java () - [DUBBO] Failed to uregister dubbo://127.0.0.1:20880/...... com.alibaba.dubbo.rpc.RpcException: Failed to unregister dubbo://127.0.0.1:20880/业务方法...... at com.alibaba.dubbo.registry.zookeeper.ZookeeperRegistry.doUnregister(ZookeeperRegistry.java:108) at com.alibaba.dubbo.registry.support.FailbackRegistry.unregister(FailbackRegistry.java:160) at com.alibaba.dubbo.registry.integration.RegistryProtocol$1.unexport(RegistryProtocol.java:130) at com.alibaba.dubbo.config.ServiceConfig.unexport(ServiceConfig.java:270) at com.alibaba.dubbo.config.spring.ServiceBean.destroy(ServiceBean.java:255) at org.springframework.beans.factory.support.DisposableBeanAdapter.destroy(DisposableBeanAdapter.java:258) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroyBean(DefaultSingletonBeanRegistry.java:538) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroySingleton(DefaultSingletonBeanRegistry.java:514) at org.springframework.beans.factory.support.DefaultListableBeanFactory.destroySingleton(DefaultListableBeanFactory.java:831) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroySingletons(DefaultSingletonBeanRegistry.java:483) at org.springframework.context.support.AbstractApplicationContext.destroyBeans(AbstractApplicationContext.java:923) at org.springframework.context.support.AbstractApplicationContext.doClose(AbstractApplicationContext.java:897) at org.springframework.context.support.AbstractApplicationContext$1.run(AbstractApplicationContext.java:811) Caused by: java.lang.NullPointerException at org.I0Itec.zkclient.ZkClient$8.call(ZkClient.java:720) at org.I0Itec.zkclient.ZkClient.retryUntilConnected(ZkClient.java:675) at org.I0Itec.zkclient.ZkClient.delete(ZkClient.java:716) at com.alibaba.dubbo.remoting.zookeeper.zkclient.ZkclientZookeeperClient.delete(ZkclientZookeeperClient.java:57) at com.alibaba.dubbo.registry.zookeeper.ZookeeperRegistry.doUnregister(ZookeeperRegistry.java:106) ... 12 more

上面需要注意的关键信息可以归结为：zookeeper客户端关闭(Closing ZkClient…)、dubbo服务关闭(Close dubbo server….)、注销dubbo的某个方法失败(Failed to uregister dubbo://127.0.0.1:20880/…) 
虽然没细探究到底怎么回事，但是感觉应该是单元测试同时加载服务端和客户端(即加载spring配置文件)，当测试方法执行完毕需要关闭服务的时候，由于先后顺序问题引发的异常。

7、再次解决办法：提供者由主容器启动，至于单元测试，就到了上面最后的彩蛋那句话了，单元测试作为客户端，只需要拿到服务端提供者的bean对象，就可以完成对提供者服务端的调用。

那么这个对象从哪里来，dubbo+zookeeper方式会在客户端配置订阅服务的配置文件，这个里面有提供者对应的bean，所以单元测试只需要加载客户端订阅配置文件即可，代码如下：

@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration({ "classpath:/spring/test-dubbo-consumer.xml" }) public class CodeRuleRPCImplDubboTest { @Autowired private UserRPC UserRPC; @Test public void testGetUserByCode() { bizCode = userRPC.getUserByCode("001"); } }

客户端订阅者配置文件：

<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:jee="http://www.springframework.org/schema/jee" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:util="http://www.springframework.org/schema/util" xmlns:task="http://www.springframework.org/schema/task" xmlns:dubbo="http://code.alibabatech.com/schema/dubbo" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-4.0.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-4.0.xsd http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd"> <!-- 消费方应用名称信息，这个相当于起一个名字，我们dubbo管理页面比较清晰是哪个应用暴露出来的 --> <dubbo:application name="SPRING_DUBBO_CONSUMER"></dubbo:application> <!-- 使用zookeeper注册中心暴露服务地址 --> <dubbo:registry address="zookeeper://127.0.0.1:2181" check="true"></dubbo:registry> <!-- 要引用的用户管理服务 --> <dubbo:reference interface="com.test.rpc.UserRPC" id="userRPC"></dubbo:reference> </beans>

 

至此以上问题解决，同时深入理解spring容器，单元测试，spring-bean之间的关系，同时也对dubbo和zookeeper加深了了解。