使用TypeTools解决泛型类型信息 [英] Resolving generic type information with TypeTools
问题描述
在下面的fromMap的实现中,我想使用 TypeTools
获得通用类型 T
的运行时类型,但是我遇到了 NullPointerException
TypeResolver.resolveRawArguments(MapperImpl.class,getClass());
中的code>.
In the implementation of fromMap below I would like to get the runtime type of the generic type T
using TypeTools
but I am stuck with a NullPointerException
in TypeResolver.resolveRawArguments(MapperImpl.class, getClass());
.
我该如何实现?
Mapper.java:
import java.util.Map;
public interface Mapper<T extends Object, S extends Map<String, Object>> {
public S toMap(T obj);
public T fromMap(S map);
}
MapperImpl.java
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.Map;
import net.jodah.typetools.TypeResolver;
public class MapperImpl<T extends Object, S extends Map<String, Object>>
implements Mapper<T, S> {
public S toMap(T obj) {
ObjectMapper objectMapper = new ObjectMapper();
Map<String, Object> map = objectMapper.convertValue(obj, Map.class);
return (S) map;
}
public T fromMap(S map) {
ObjectMapper objectMapper = new ObjectMapper();
Class<?>[] ts = TypeResolver.resolveRawArguments(MapperImpl.class, getClass());
Class<T> classT = (Class<T>) ts[0];
T obj = objectMapper.convertValue(map, classT);
return obj;
}
推荐答案
TypeTools或Java中的任何通用类型解析,始终要求在类型定义中捕获类型实参.只要将MapperImpl子类化,以便在类型定义中捕获 T
和 S
的值,您尝试执行的操作就可以正常工作.例如:
TypeTools, or any generic type resolution in Java, always required that the type arguments be captured in a type definition. What you're attempting to do will work fine so long as MapperImpl is subclassed so that the value of T
and S
are captured in a type definition. Ex:
public class FooMapper extends MapperImpl<Foo, ArrayList<String, Object>> {}
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