我正在使用下一个推土机自定义转换器
public class MyCustomDozerConverter extends DozerConverter<MyObject, String> {
@Autowired
private AppConfig appConfig;
public MyCustomDozerConverter() {
super(MyObject.class, String.class);
}
@Override
public String convertTo(MyObject source, String destination) {
String myProperty = appConfig.getWhatever();
// business logic
return destination;
}
@Override
public MyObject convertFrom(String source, MyObject destination) {
// business logic
return null;
}
}
我的问题是当它在转换器中通过convertTo方法时,我总是得到带有null值的appConfig实例,这当然会导致空指针异常
注意:我的spring boot类上面有这些注释:
@SpringBootApplication
@EnableAutoConfiguration
@ComponentScan({"com.xxx"})
@EntityScan("com.xxx")
@EnableJpaRepositories("com.xxx")
答案 0 :(得分:2)
我通过下一个技巧解决了这个问题:
1-使用带有appConfig属性的static。
2-弹簧实例化,所以当推土机使用默认的空构造函数时,它会找到appConfig 已经是一个值(在春天之前分配给它)
以下是我用于此的代码:
@Component //import org.springframework.stereotype.Component;
public class MyCustomDozerConverter extends DozerConverter<MyObject, String> {
private static AppConfig appConfig;
// dozer needs this constructor to create an instance of converter (so it's a mandatory constructor)
public MyCustomDozerConverter() {
super(MyObject.class, String.class);
}
@Autowired // Spring will pass appConfig to constructor
public MyCustomDozerConverter(AppConfig appConfig) {
this();
this.appConfig = appConfig;
}
@Override
public String convertTo(MyObject source, String destination) {
String myProperty = appConfig.getWhatever();
// business logic
return destination;
}
@Override
public MyObject convertFrom(String source, MyObject destination) {
// business logic
return null;
}
}
更新:另一种解决方案
另一个技巧是使用Spring ApplicationContextAware从getBean方法获取单例对象:
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
@Component
public class ApplicationContextHolder implements ApplicationContextAware {
private static ApplicationContext context;
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
context = applicationContext;
}
public static ApplicationContext getContext() {
return context;
}
}
然后在AppConfig类中创建一个静态方法,并返回与所需类型匹配的单个bean的实例:
import org.springframework.context.annotation.Configuration;
import com.tripbru.ms.experiences.ApplicationContextHolder;
@Configuration
public class AppConfig {
// Static method used to return an instatnce
public static AppConfig getInstance() {
return ApplicationContextHolder.getContext().getBean(AppConfig.class);
}
// Properties
}
然后通过 AppConfig.getInstance();
直接在推土机转换器内调用它public class MyCustomDozerConverter extends DozerConverter<MyObject, String> {
private static AppConfig appConfig;
public MyCustomDozerConverter() {
super(MyObject.class, String.class);
appConfig = AppConfig.getInstance(); // Here are we intializing it by calling the static method we created.
}
@Override
public String convertTo(MyObject source, String destination) {
String myProperty = appConfig.getWhatever();
// business logic
return destination;
}
@Override
public MyObject convertFrom(String source, MyObject destination) {
// business logic
return null;
}
}
答案 1 :(得分:0)
尝试构造函数依赖注入
private AppConfig appConfig;
@Autowired
MyCustomerDozerConverter(AppConfig appConfig)
{
this.appConfig = appConfig;
}
答案 2 :(得分:0)
您可以在CustomConverter中放置以下行,以便Spring对其进行自动布线。
public class MyCustomDozerConverter extends DozerConverter<MyObject, String> {
@Autowired
private AppConfig appConfig;
public MyCustomDozerConverter() {
super(MyObject.class, String.class);
SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);
}
...
}