When using Spring Boot for a project, Jackson came as default to serialize objects back and from Jsons. I realize that Jackson fails if you don't have public accessors, e.g., getters/setters, or public fields in your POJO.
The behavior is different when I switch to Gson. It detects all fields regardless of their visibility. For this reason, I ended up using Gson.
I felt a little uncomfortable about switching my POJO access rules; It would force some refactoring in the project structure.
So, no problems using Gson, but is there a way of change Jackson's behavior?
Jackson does support reading values from private member fields, but does not do it by default.
You can configure the behavior globally in the Spring Boot config like
jackson:
visibility.field: any
visibility.getter: none
visibility.setter: none
visibility.is-getter: none
(this config will only look for member fields and no longer check get, set and is methods)
You could also use the #JsonAutoDetect annotation to do the same setting for a specific class.
Try to set visibility at ObjectMapper level,
ObjectMapper mapper = new ObjectMapper();
mapper.setVisibility(PropertyAccessor.ALL, Visibility.NONE);
mapper.setVisibility(PropertyAccessor.FIELD, Visibility.ANY);
Related
In my spring application in WebMvcConfigurerAdapter, CustomObjectMapper is added in HttpMessageConverter. The CustomObjectMapper has setSerializationInclusion(Include.NON_NULL). For 1 particular pojo returned via Spring's ResponseBody I want null properties to be returned as well. I cannot change global setting as it will impact all controllers endpoints. Any suggestions ?
You can create a mixin for the Pojo of interest and set the mixin on your CustomObjectMapper. This other answer shows exactly how to do this.
I have a simple persistent pojo like:
public class Peristent {
private String unsafe;
}
I use Spring Data mongoTemplate to persist and fetch the above object. I also need to encrypt the Persistent.unsafe variable and store a complex representation of that in backend, everytime I try to save Persistent object.
Can I annotate Persistent, or provide some sort of hooks where I can make the aforementioned translations without me having to do that in the Pojo code manually. This has to happen automatically during mongoTemplate.insert.
Spring Data currently only support Type based conversions. There is an issue for supporting property based conversion, which you might want to track.
Therefore annotating won't work. What you could do is, create use a separate class for the property, which just wraps the String and register a custom converter for that type. See http://docs.spring.io/spring-data/data-mongo/docs/1.10.4.RELEASE/reference/html/#mongo.custom-converters for details, how to do that.
I'm using the Spring LDAP (docs) library in a Grails application. I have a class annotated with the #Entry annotation, so it is mapped to an LDAP server. This all works quite beautifully.
However, when I add the Grails #Validateable annotation (to enable validating the LDAP class similarly to Grails domain classes) and attempt to retrieve data from LDAP (i.e. a findAll operation on the LdapUserRepo, or similar), I get the following exception:
Message: Missing converter from class java.lang.String to interface org.springframework.validation.Errors, this is needed for field errors on Entry class com.ldap.portal.LdapUser
Basically, it seems like the AST transformation performed by the #Validateable annotation is producing extra fields (namely the errors field) on the LdapUser object. It appears that Spring LDAP, in processing the #Entry logic, assumes a default mapping for the fields property (probably interpreting it as a string field on the LDAP object). When it gets nothing from the LDAP server, it attempts to set the field of type ValidationErrors to a value of type String -- an empty string.
I did some looking in github and found this code that seems relevant and may support my theory.
My question is: is this behavior expected for annotations, and how can one prevent fields added by one annotation from being inappropriately processed by another annotation?
At present the best workaround I've come up with for my specific issue is to add an errors field to my LdapUser object and mark it as transient (so that LDAP ignores it):
#Transient
ValidationErrors errors
I have some trouble using Jackson 2.1 in an OSGi environment, when deserializing a class that way:
ObjectMapper mapper = new ObjectMapper();
User user = mapper.readValue(new File("user.json"), User.class);
class User {
public Class clazz = org.example.MyClass.class;
}
Because Jackson is in a different bundle as my custom classes I want to deserialize, I often get a java.lang.ClassNotFoundException - usually on MyClass1 or MyClass2.
I traced it back to the class com.fasterxml.jackson.databind.util.ClassUtil which uses Class.forName(..) for retrieving a class for deserializing. Because of the different class-loaders on OSGI it only sees the classes of the JRE and of Jackson but not my custom classes.
Is there a simple way to make Jackson find all the required custom classes (I have dozens of them), e.g by adding a class-loader?
As the client of Jackson you have visibility of the classes that you want to deserialize into. The trick is to pass these classes into Jackson, rather than force Jackson to use dynamic reflection to find the classes.
The Jackson documentation indicates that the method ObjectMapper.readValue can take a Class object as its parameter. If you use this method then Jackson should not need to call Class.forName(). The docs give the following example:
ObjectMapper mapper = new ObjectMapper();
User user = mapper.readValue(new File("user.json"), User.class);
Here, User is the domain class which is visible to your client but not to Jackson. This invocation should work fine in OSGi... if it does not then I would suggest Jackson may have a bug.
Let's imagine we have such a component in Spring:
#Component
public class MyComponent {
#Value("${someProperty}")
private String text;
}
If we define the property placeholder:
<context:property-placeholder location="classpath:myProps.properties"/>
And myPropos.properties contains the value for someProperty the value will be injected to the text field when the context is initialized. That's quite simple and easy.
But let's say that I have a service that enables user to change the value of the someProperty:
public void changeProp(String name, String newValue);
Is there a chance I can re-inject the newValue to text field. I mean it should be quite straight forward.. Basically it's nothing different than the after-initialization injection. I can not imagine that Spring does not have support for this? Can I fire some event or something?
I could do this on my own basically, but I wander is it maybe something there already? If not does anyone know what Spring class is in fact handling the injections at the first place? I could probably reuse the code there do perform this on my own if a solution does not exists.
I expect spring does not have a support for this, because the normal injection is done while creating the bean, but not will it is put in service.
Anyway: in this blog entry "Reloadable Application Properties with Spring 3.1, Java 7 and Google Guava", you can find the idea for an solution.
The key idea is to use a post processor to build a list of all fields with property fields. And if the properties are changed on can use this list to update the fields.