理解 Spring 的 FactoryBean 和 ContextAware 接口。
FactoryBean
一句话就是 FactoryBean 用于返回其他对象实例的，而不是自身类型的实例。
public class Tool {
private int id;
// standard constructors, getters and setters
}
public class ToolFactory implements FactoryBean<Tool> {
private int factoryId;
private int toolId;
@Override
public Tool getObject() throws Exception {
return new Tool(toolId);
}
@Override
public Class<?> getObjectType() {
return Tool.class;
}
@Override
public boolean isSingleton() {
return false;
}
// standard setters and getters
}
注册 Tool:
<!-- factorybean-spring-ctx.xml -->
<beans>
<bean id="tool" class="com.baeldung.factorybean.ToolFactory">
<property name="factoryId" value="9090"/>
<property name="toolId" value="1"/>
</bean>
</beans>
使用注解注册：
@Bean(name = "tool")
ToolFactory toolFactory() {
ToolFactory factory = new ToolFactory();
factory.setFactoryId(7070);
factory.setToolId(2);
return factory;
}
使用 Tool:
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "classpath:factorybean-spring-ctx.xml" })
public class FactoryBeanXmlConfigTest {
@Autowired
private Tool tool;
@Test
public void testConstructWorkerByXml() {
assertThat(tool.getId(), equalTo(1));
}
}
访问 ToolFactory，在 bean id 前面添加 &:
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "classpath:factorybean-spring-ctx.xml" })
public class FactoryBeanXmlConfigTest {
@Resource(name = "&tool")
private ToolFactory toolFactory;
@Test
public void testConstructWorkerByXml() {
assertThat(toolFactory.getFactoryId(), equalTo(9090));
}
}
和 BeanFactory 的区别
除了 FactoryBean，还有一个 BeanFactory 的接口及其实现。