一、先说一个结论：单元与主项目的容器是隔离的，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 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 getBean(Class 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 contextList = new ArrayList (); 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 list = new ArrayList (); list.addAll(contextList); for (int i = 0; contextFile != null && i < contextFile.length; i++) { list.add(contextFile[i]); } 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 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 getBean(Class 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