java – 解析自定义控制器中的实体URI(Spring HATEOAS)
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我有一个基于spring-data-rest的项目,它也有一些自定义端点.
为了发送POST数据,我正在使用json
{
"action": "REMOVE",
"customer": "http://localhost:8080/api/rest/customers/7"
}
这对于s??pring-data-rest来说很好,但不适用于自定义控制器.
例如：
public class Action {
public ActionType action;
public Customer customer;
}
@RestController
public class ActionController(){
@Autowired
private ActionService actionService;
@RestController
public class ActionController {
@Autowired
private ActionService actionService;
@RequestMapping(value = "/customer/action", method = RequestMethod.POST)
public ResponseEntity<ActionResult> doAction(@RequestBody Action action){
ActionType actionType = action.action;
Customer customer = action.customer;//<------There is a problem
ActionResult result = actionService.doCustomerAction(actionType, customer);
return ResponseEntity.ok(result);
}
}
我打电话的时候
curl -v -X POST -H "Content-Type: application/json" -d '{"action": "REMOVE","customer": "http://localhost:8080/api/rest/customers/7"}' http://localhost:8080/customer/action
我有一个答案
{
"timestamp" : "2016-05-12T11:55:41.237+0000",
"status" : 400,
"error" : "Bad Request",
"exception" : "org.springframework.http.converter.HttpMessageNotReadableException",
"message" : "Could not read document: Can not instantiate value of type [simple type, class model.user.Customer] from String value ('http://localhost:8080/api/rest/customers/7'); no single-String constructor/factory method\n at [Source: java.io.PushbackInputStream@73af10c6; line: 1, column: 33] (through reference chain: api.controller.Action[\"customer\"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not instantiate value of type [simple type, class logic.model.user.Customer] from String value ('http://localhost:8080/api/rest/customers/7'); no single-String constructor/factory method\n at [Source: java.io.PushbackInputStream@73af10c6; line: 1, column: 33] (through reference chain: api.controller.Action[\"customer\"])",
"path" : "/customer/action"
* Closing connection 0
}
bacause case spring无法将URI转换为Customer实体.
有没有办法使用spring-data-rest机制通过URI解析实体？
我只有一个想法 – 使用自定义JsonDeserializer和解析URI来提取entityId并向存储库发出请求.但是这个策略对我没有帮助,如果我有像“http://localhost:8080/api/rest/customers/8/product”这样的URI,那我没有product.Id值.
解决方法:
我很长时间以来一直遇到同样的问题并通过以下方式解决了. @Florian走在正确的轨道上,由于他的建议,我找到了一种方法让转换自动完成.需要几件：
>转换服务,用于实现从URI到实体的转换(利用框架提供的UriToEntityConverter)
>解串器,用于检测何时适合调用转换器(我们不想弄乱默认的SDR行为)
>一个定制的杰克逊模块,将一切推向SDR
对于第1点,可以将实施范围缩小到以下内容
import org.springframework.context.ApplicationContext;
import org.springframework.data.mapping.context.PersistentEntities;
import org.springframework.data.repository.support.DomainClassConverter;
import org.springframework.data.rest.core.UriToEntityConverter;
import org.springframework.format.support.DefaultFormattingConversionService;
public class UriToEntityConversionService extends DefaultFormattingConversionService {
private UriToEntityConverter converter;
public UriToEntityConversionService(ApplicationContext applicationContext, PersistentEntities entities) {
new DomainClassConverter<>(this).setApplicationContext(applicationContext);
converter = new UriToEntityConverter(entities, this);
addConverter(converter);
}
public UriToEntityConverter getConverter() {
return converter;
}
}
对于第2点,这是我的解决方案
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.deser.BeanDeserializerBuilder;
import com.fasterxml.jackson.databind.deser.BeanDeserializerModifier;
import com.fasterxml.jackson.databind.deser.ValueInstantiator;
import com.fasterxml.jackson.databind.deser.std.StdValueInstantiator;
import your.domain.RootEntity; // <-- replace this with the import of the root class (or marker interface) of your domain
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.data.mapping.PersistentEntity;
import org.springframework.data.mapping.context.PersistentEntities;
import org.springframework.data.rest.core.UriToEntityConverter;
import org.springframework.util.Assert;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.Optional;
public class RootEntityFromUriDeserializer extends BeanDeserializerModifier {
private final UriToEntityConverter converter;
private final PersistentEntities repositories;
public RootEntityFromUriDeserializer(PersistentEntities repositories, UriToEntityConverter converter) {
Assert.notNull(repositories, "Repositories must not be null!");
Assert.notNull(converter, "UriToEntityConverter must not be null!");
this.repositories = repositories;
this.converter = converter;
}
@Override
public BeanDeserializerBuilder updateBuilder(DeserializationConfig config, BeanDescription beanDesc, BeanDeserializerBuilder builder) {
PersistentEntity<?, ?> entity = repositories.getPersistentEntity(beanDesc.getBeanClass());
boolean deserializingARootEntity = entity != null && RootEntity.class.isAssignableFrom(entity.getType());
if (deserializingARootEntity) {
replaceValueInstantiator(builder, entity);
}
return builder;
}
private void replaceValueInstantiator(BeanDeserializerBuilder builder, PersistentEntity<?, ?> entity) {
ValueInstantiator currentValueInstantiator = builder.getValueInstantiator();
if (currentValueInstantiator instanceof StdValueInstantiator) {
EntityFromUriInstantiator entityFromUriInstantiator =
new EntityFromUriInstantiator((StdValueInstantiator) currentValueInstantiator, entity.getType(), converter);
builder.setValueInstantiator(entityFromUriInstantiator);
}
}
private class EntityFromUriInstantiator extends StdValueInstantiator {
private final Class entityType;
private final UriToEntityConverter converter;
private EntityFromUriInstantiator(StdValueInstantiator src, Class entityType, UriToEntityConverter converter) {
super(src);
this.entityType = entityType;
this.converter = converter;
}
@Override
public Object createFromString(DeserializationContext ctxt, String value) throws IOException {
URI uri;
try {
uri = new URI(value);
} catch (URISyntaxException e) {
return super.createFromString(ctxt, value);
}
return converter.convert(uri, TypeDescriptor.valueOf(URI.class), TypeDescriptor.valueOf(entityType));
}
}
}
然后对于第3点,在自定义RepositoryRestConfigurerAdapter中,
public class MyRepositoryRestConfigurer extends RepositoryRestConfigurerAdapter {
@Override
public void configureJacksonObjectMapper(ObjectMapper objectMapper) {
objectMapper.registerModule(new SimpleModule("URIDeserializationModule"){
@Override
public void setupModule(SetupContext context) {
UriToEntityConverter converter = conversionService.getConverter();
RootEntityFromUriDeserializer rootEntityFromUriDeserializer = new RootEntityFromUriDeserializer(persistentEntities, converter);
context.addBeanDeserializerModifier(rootEntityFromUriDeserializer);
}
});
}
}
这对我来说很顺利,并且不会干扰框架的任何转换(我们有许多自定义端点).在第2点中,目的是仅在以下情况下从URI启用实例化：
>被反序列化的实体是根实体(因此没有属性)
>提供的字符串是一个实际的URI(否则它只是回到默认行为)
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