Spring Data Rest Field converter

2019-04-11 02:20发布

问题:

I am having a hard time using my custom converters on spring data REST project (controller free application and strictly java configuration).

I have two Entities, an Employee and a State. The relationship is @ManyToOne, I am sure we all know that. Anyway, the problem is converting the state field (field name is state) from String to a State object and setState() in the Employee class for persistence to a database.

package com.hr.domain;

@Entity
public class Employee implements Serializable {

   private static final long serialVersionUID = 1L;

   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   @Column(name = "state_id", nullable = true)
   private Long id;
   private String firstname;
   private State state;

   @StateConverter
   @ManyToOne(fetch = FetchType.LAZY)
   @JoinColumn(name = "employee_state_id_fk", nullable = false, insertable = true, updatable = true)
   private State state;

   //GETTERS AND SETTERS
   public String getFirstname() {
      return firstname();
   }

   public void setFirstname(String firstname) {
      this.firstname = firstname;
   }

   public String getState() {
    return state();
   }

   public void setState(State state) {
     this.state = state;
   }

   //HASHCODES AND EQUALS

}


package com.hr.domain;

@Entity
public class State implements Serializable {

   private static final long serialVersionUID = 1L;

   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   @Column(name = "state_id", nullable = true)
   private Long id;
   private String state_name;

   //GETTERS AND SETTERS

  //TO STRING
  @Override
  public String toString() {
    return "State [id=" + id + ", state_name=" + state_name + "]";
  }       

}

I have registered my converter with the conversion service but still cant get the String to be converter to State object on form submit.

@Bean//(name="conversionService")
public ConversionService getConversionService() {       
    ConversionServiceFactoryBean bean = new ConversionServiceFactoryBean();
    bean.setConverters(getConverters());
    bean.afterPropertiesSet();
    ConversionService object = bean.getObject();
    System.out.println(object);
    return object;
}

private Set<Converter> getConverters() {    
    Set<Converter> converters = new HashSet<Converter>();
    converters.add(new StringToStateTypeConverter());
    return converters;      
}

This is my StateConverter

@Component
@StateConverter
public class StringToStateTypeConverter implements Converter<String, State> {

    @Autowired
    StateRepository repository;

    public State convert(String source) {
        return repository.findOne(new Long(source));
    }

}

On submission, I get this error:

Caused by: org.springframework.core.convert.ConversionFailedException: Failed to convert from type java.net.URI to type com.hr.domain.State for value 'AB';

Any form of help will be appreciated.

May the force be with you Regards.

Here is the Error trace

17:21:29,975 ERROR [org.springframework.data.rest.webmvc.AbstractRepositoryRestController] (default task-13) Could not read JSON: Failed to convert from type java.net.URI to type com.hr.domain.State for value 'AB'; nested exception is java.lang.IllegalArgumentException: Cannot resolve URI AB. Is it local or remote? Only local URIs are resolvable. (through reference chain: com.hr.domain.Employee["State"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Failed to convert from type java.net.URI to type com.hr.domain.State for value 'AB'; nested exception is java.lang.IllegalArgumentException: Cannot resolve URI AB. Is it local or remote? Only local URIs are resolvable. (through reference chain: com.hr.domain.Employee["State"]): org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Failed to convert from type java.net.URI to type com.hr.domain.State for value 'AB'; nested exception is java.lang.IllegalArgumentException: Cannot resolve URI AB. Is it local or remote? Only local URIs are resolvable. (through reference chain: com.hr.domain.Employee["State"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Failed to convert from type java.net.URI to type com.hr.domain.State for value 'AB'; nested exception is java.lang.IllegalArgumentException: Cannot resolve URI AB. Is it local or remote? Only local URIs are resolvable. (through reference chain: com.hr.domain.Employee["State"])
    at org.springframework.http.converter.json.MappingJackson2HttpMessageConverter.readJavaType(MappingJackson2HttpMessageConverter.java:228) [spring-web-4.0.5.RELEASE.jar:4.0.5.RELEASE]

...........
Caused by: com.fasterxml.jackson.databind.JsonMappingException: Failed to convert from type java.net.URI to type com.hr.domain.State for value 'AB'; nested exception is java.lang.IllegalArgumentException: Cannot resolve URI AB. Is it local or remote? Only local URIs are resolvable. (through reference chain: com.hr.domain.Employee["State"])
    at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:232) [jackson-databind-2.3.3.jar:2.3.3]
    at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:197) [jackson-databind-2.3.3.jar:2.3.3]

Caused by: org.springframework.core.convert.ConversionFailedException: Failed to convert from type java.net.URI to type com.hr.domain.State for value 'AB'; nested exception is java.lang.IllegalArgumentException: Cannot resolve URI AB. Is it local or remote? Only local URIs are resolvable.
    at org.springframework.data.rest.core.UriToEntityConverter.convert(UriToEntityConverter.java:106) [spring-data-rest-core-2.1.0.RELEASE.jar:]
    at org.springframework.data.rest.webmvc.json.PersistentEntityJackson2Module$UriStringDeserializer.deserialize(PersistentEntityJackson2Module.java:359) [spring-data-rest-webmvc-2.1.0.RELEASE.jar:]

Caused by: java.lang.IllegalArgumentException: Cannot resolve URI AB. Is it local or remote? Only local URIs are resolvable.
    ... 94 more

回答1:

You a registering a new ConversionService. It replaces the default one that spring registers by default with a lot of converters that are generally assumed to be present. And you create a new converter instead of using your configured bean. You should instead :

  • register the default conversion service of spring with all its default converters
  • add you converter to this one

Your conversion service initialization could look like :

private @Autowired StringToStateTypeConverter stringToStateTypeConverter;

@Bean//(name="conversionService")
public ConversionService getConversionService() {       
    ConversionServiceFactoryBean bean = new DefaultFormattingConversionService();
    bean.addConverter(String.class, State.class, stringToStateTypeConverter);
    return bean;
}

EDIT

As the error come from a problem of conversion from URI to State, you could try to add a converter from URI to State (assuming your repository has a method findByName to find a State by its name:

@Component
@StateConverter
public class URIToStateTypeConverter implements Converter<URI, State> {
    @Autowired
    StateRepository repository;

    public State convert(URI uri) {
        String source = uri.toString();
        try {
            long id = Long.valueOf(source);
            return repository.findOne(id);
        } catch (NumberFormatException e) { // should be a name ??
            return repository.findByName(source);
        }
    }
}

And the conversion service initialization would become :

private @Autowired StringToStateTypeConverter stringToStateTypeConverter;
private @Autowired URIToStateTypeConverter uriToStateTypeConverter;

@Bean//(name="conversionService")
public ConversionService getConversionService() {       
    ConversionServiceFactoryBean bean = new DefaultFormattingConversionService();
    bean.addConverter(String.class, State.class, stringToStateTypeConverter);
    bean.addConverter(URI.class, State.class, uriToStateTypeConverter);
    return bean;
}

But I'm not sure if it will be used by spring-data-rest