Spring MVC&自定义JsonSerializer [英] Spring MVC & custom JsonSerializer
问题描述
我正在使用带有MVC的Spring 5.0并为实体提供自定义（de）序列化程序，例如
I'm using Spring 5.0 with MVC and have a custom (de)serializer for an entity, e.g.
@JsonDeSerialize(using = RoleDeserializer.class)
public class Role implements Serializable {
....
和反序列化我有（StdDesializer不会改变任何东西）
and for deserializing I have (StdDesializer won't change anything)
public class RoleDeserializer extends JsonDeserializer<Role> {
EntityManager em;
public RoleDeserializer(EntityManager em) {
this.em = em;
}
....
这给了我一个例外
MappingJackson2HttpMessageConverter:205 Failed to evaluate Jackson deserialization for type [[simple type, class test.Role]]: c
om.fasterxml.jackson.databind.JsonMappingException: Class test.RoleDeserializer has no default (no arg) constructor
但不知何故，我需要那个构造函数，因为如果我这样做
but somehow I need to have that constructor since if I do it like
public class RoleDeserializer extends JsonDeserializer<Role> {
@PersitenceContext
EntityManager em;
....
em上的自动注释 with @PersitenceContext 不起作用，因为它没有用Spring注入，即没有初始化。
The automatic annotation on em with @PersitenceContext does not work because it is not injected with Spring, i.e. not initialized.
备注：在建议之后，我无法解决此问题。 link <中解释了此行为的原因/ a> - 但这并没有摆脱异常： - /
Remark: Following the suggestions I could not resolve the issue. The reason of the behavior is explained in link - but this does not get rid of the Exceptions :-/
非常感谢帮助。
推荐答案
在提示我的问题之后，我想出了如何在Spring 5.0中解决这个问题（最有可能在4.1.1中） - 没有XML：
After the hint to my question I figured out how to resolve this issue in Spring 5.0 (most likely as well in 4.1.1) - without XML:
@EnableWebMvc
@Configuration
public class WebConfig implements WebMvcConfigurer {
@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
final HashMap<Class<?>, JsonDeserializer<?>> map = new HashMap<>();
map.put(Role.class, new RoleDeserializer());
// more classes could be easily attached the same way...
builder.deserializersByType(map);
converters.add(new MappingJackson2HttpMessageConverter(builder.build()));
}
}
此后注释 @自动装配的或 @PersistenceContext 在课程中按预期工作:-)
Thx for the support！
after this the annotations @Autowired or @PersistenceContext work as expected in the classes :-)
Thx for the support!
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