new 出的物件無法使用 @Autowired裝配進來的屬性，會報null
阿新 • • 發佈：2018-12-23
new 出的物件,無法呼叫@Autowired進入的spring bean
(2011-02-11 17:55:54) @Autowired來的spring 下的bean,則當前類必須也是spring bean才能呼叫它,不能用new Xxx()來獲得物件,這種方式獲得的物件無法呼叫其內的@autowired的bean
轉載|
1. 類1 加入spring pool |
public class PersonServiceImpl implements PersonService{ public void save(){ System.out.println("This is save for test spring"); } public List<String> findAll(){ List<String> retList = new ArrayList<String>(); for(int i=1;i<10;i++){ retList.add("test"+i); } return retList; } } 加入spring pool <bean id="personServiceImpl" class="com.machome.testtip.impl.PersonServiceImpl" > </bean> |
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2.類2 autowired類1, 並且也加入spring pool |
public class ProxyPServiceImpl implements ProxyPService { public void save(){ System.out.print("this is proxy say:"); personService.save(); } public List<String> findAll(){ System.out.print("this is proxy say:"); return personService } @Autowired PersonService personService; } |
| 3.直接new類2,則執行其方法時出null pointer錯誤 |
ProxyPService proxyPService = new ProxyPServiceImpl(); proxyPService.save(); 執行報錯: java.lang.NullPointerException at com.machome.testtip.impl.ProxyPServiceImpl.save(ProxyPServiceImpl.java:18) at com.machome.testtip.TestSpring2.testSave(TestSpring2.java:34) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) |
| 4.解決:用spring 方式獲取類2的bean,再執行其方法,沒問題 |
ProxyPService proxyPService = null; try { String[] confFile = {"spring.xml"}; ctx = new ClassPathXmlApplicationContext(confFile); proxyPService = (ProxyPService)ctx.getBean("ProxyPServiceImpl"); } catch (Exception e) { e.printStackTrace(); } proxyPService.save(); 執行: this is proxy say:This is save for test spring |