Struts2 JSON Plugin not working with “lazy” data
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22-07-2019 - |
Question
I have an Entity with a OneToOne relation that is fetched lazily:
@Entity
public class Person {
@Id
private Integer id;
@Column(length=60)
private String address;
@OneToOne(fetch=FetchType.LAZY)
@JoinColumn(name="idProvince")
private Province province;
}
This is the test I do, trying to get all the entities and to serialize them as JSON, using the JSONUtil class in JSONPlugin (the 'official' json plugin for Struts 2):
List<Person> people = personService.findAll();
String result = JSONUtil.serialize(people);
System.out.println(result);
And this is the exception I get (the same exception when I use this plugin with a Struts2 Action and the @JSON annotation):
com.googlecode.jsonplugin.JSONException: java.lang.IllegalAccessException:
Class com.googlecode.jsonplugin.JSONWriter can not access a member of class
org.postgresql.jdbc4.AbstractJdbc4Statement with modifiers "public"
at com.googlecode.jsonplugin.JSONWriter.bean(JSONWriter.java:237)
at com.googlecode.jsonplugin.JSONWriter.process(JSONWriter.java:159)
at com.googlecode.jsonplugin.JSONWriter.value(JSONWriter.java:125)
at com.googlecode.jsonplugin.JSONWriter.array(JSONWriter.java:407)
at com.googlecode.jsonplugin.JSONWriter.process(JSONWriter.java:149)
at com.googlecode.jsonplugin.JSONWriter.value(JSONWriter.java:125)
at com.googlecode.jsonplugin.JSONWriter.write(JSONWriter.java:93)
at com.googlecode.jsonplugin.JSONWriter.write(JSONWriter.java:76)
at com.googlecode.jsonplugin.JSONUtil.serialize(JSONUtil.java:62)
...
I am using Hibernate and the same code above works when I change fetch=FetchType.EAGER. I think lazy loading generates a proxy-object, and that makes it fail.
My question is : Is it possible to serialize objects that contain lazily loaded attributes ?
Solution
I had the same problem while using JSON-lib, and it is indeed because the object is a proxy.
I found Google-Gson handles serialization of Hibernate objects better, but of course it has its own quirks, so your mileage may vary.
OTHER TIPS
Detach the Entities from the Hibernate & then serialize them.