spring中使用autowire特性时注意

素颜马尾好姑娘i 2022-08-24 11:27 135阅读 0赞

spring中可以只用autowire="byName"或者"byType"来提供自动注入。但是大家有一点还需要注意，那就是它不支持基本数据类型(String，int，long等)的自动注入。例如  
JAVA类：

1.  public class TestBean \{
2.  private String name;
3.  private Long age;
4.  private String fullName;
5.  private TestBean2 testBean2;
6.  
7.  public void setTestBean2(TestBean2 testBean2) \{
8.  this.testBean2 = testBean2;
9.  \}
10. public TestBean2 getTestBean2() \{
11. return testBean2;
12. \}
13. public void setFullName(String fullName) \{
14. this.fullName = fullName;
15. \}
16. public String getFullName() \{
17. return fullName;
18. \}
19. 
20. public void setAge(Long age) \{
21. this.age = age;
22. \}
23. 
24. public Long getAge() \{
25. return age;
26. \}
27. 
28. public void setName(String name) \{
29. this.name = name;
30. \}
31. 
32. public String getName() \{
33. return name;
34. \}
35. \}
36.

JAVA类2：

1.  public class TestBean2 \{
2.  public String getString()\{
3.  return "testB";
4.  \}
5.  \}

配置文件：

1.  <beans default-autowire="byName">
2.  
3.  <bean id="testBean" class="TestBean">
4.  <property name="fullName">
5.  <value>fullName</value>
6.  </property>
7.  </bean>
8.  <bean id="name" class="java.lang.String">
9.  <constructor-arg>
10. <value>hell</value>
11. </constructor-arg>
12. </bean>
13. <bean id="age" class="java.lang.Long">
14. <constructor-arg>
15. <value>20</value>
16. </constructor-arg>
17. </bean>
18. <bean id="testBean2" class="TestBean2"/>
19. </beans>

测试类：

1.  import org.springframework.context.support.ClassPathXmlApplicationContext;
2.  
3.  public class Test \{
4.  public static void main(String\[\] args) \{
5.  ClassPathXmlApplicationContext t = new ClassPathXmlApplicationContext(
6.  "test.xml");
7.  TestBean bean = (TestBean) t.getBean("testBean");
8.  System.out.println("name:" \+ bean.getName() + " age:" \+ bean.getAge()
9.  \+ " fullName :" \+ bean.getFullName() + " testBean2"
10. \+ bean.getTestBean2().getString());
11. \}
12. 
13. \}

输出的结果是：  
name:null age:null fullName :fullName testBean2:testB  
  
  
spring源码中排除基本类型的代码（源码来自：org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory类）在：

1.  protected String\[\] unsatisfiedNonSimpleProperties(AbstractBeanDefinition mbd, BeanWrapper bw) \{
2.  Set result = new TreeSet();
3.  PropertyValues pvs = mbd.getPropertyValues();
4.  PropertyDescriptor\[\] pds = bw.getPropertyDescriptors();
5.  for (int i = 0; i < pds.length; i++) \{
6.  if (pds\[i\].getWriteMethod() != null && !isExcludedFromDependencyCheck(pds\[i\]) &&
7.  !pvs.contains(pds\[i\].getName()) && !BeanUtils.isSimpleProperty(pds\[i\].getPropertyType())) \{
8.  result.add(pds\[i\].getName());
9.  \}
10. \}
11. return StringUtils.toStringArray(result);
12. \}
13.

请注意以上紫色部分。而这个 unsatisfiedNonSimpleProperties方法都是在自动注入时调用。所以基本类型不会被注入。