自动装配Autowired注解不定制推土机转换器内部工作

Question

我使用未来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，当它通过转换器内的ConvertTo方法，我总是得到AppConfig的实例与空值的当然导致空指针异常

注：我的春天引导类有以上这些注释：

@SpringBootApplication 
@EnableAutoConfiguration 
@ComponentScan({"com.xxx"}) 
@EntityScan("com.xxx") 
@EnableJpaRepositories("com.xxx") 

Answer 1

我解决了这个由下一招：

1-使用静态在AppConfig财产。

2-初始化它通过弹簧，当推土机使用默认的空构造它会找到的AppConfig有 值已经（其中弹簧之前分配给它）

这里是我用这个代码：

@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 ApplicationContextA洁具得到的getBean方法的单一对象：

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; 
    } 
} 

然后创建的AppConfig类中的静态方法，并返回一个bean的实例相匹配所需的类型：

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 
} 

然后调用它直接内推土机转换器AppConfig.getInstance（）;

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; 
    } 
} 

Answer 2

尝试构造函数依赖注入

private AppConfig appConfig; 
@Autowired 
MyCustomerDozerConverter(AppConfig appConfig) 
{ 
    this.appConfig = appConfig; 
}