title: Persisting Objects containing Objects with spring-data-mongodb
body: <p>Below is a follow-up question to <a href="https://stackoverflow.com/questions/13832188">Question 13832188</a>:</p>
  
  <p>I'm using <code>spring-data-mongodb</code> version <code>1.1.1.RELEASE</code>.  I am able to persist an object if all the member variables are primitive types, even if the names of the <code>@PersistenceConstructor</code> arguments don't match exactly the names of the member variables by using the <code>@Field</code> and <code>@Value</code> annotations.  </p>
  
  <p>However, I get a <code>MappingInstantiationException</code> when I try to persist objects that contain other objects. My questions:</p>
  
  <ul>
  <li>Is this a bug in <code>spring-data-mongodb</code> or am I doing something wrong?</li>
  <li>What needs to change so that I can properly persist objects containing objects?</li>
  </ul>
  
  <p>.</p>
  
  <pre><code>org.springframework.data.mapping.model.MappingInstantiationException: Could not instantiate bean class [com.recorder.TestRecorder2$ObjectContainer]: Illegal arguments for constructor; nested exception is java.lang.IllegalArgumentException: argument type mismatch
      at org.springframework.data.convert.ReflectionEntityInstantiator.createInstance(ReflectionEntityInstantiator.java:77)
      at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:229)
      at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:209)
      at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:173)
      at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:169)
      at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:72)
      at org.springframework.data.mongodb.core.MongoTemplate$ReadDbObjectCallback.doWith(MongoTemplate.java:1820)
      at org.springframework.data.mongodb.core.MongoTemplate.executeFindMultiInternal(MongoTemplate.java:1542)
      at org.springframework.data.mongodb.core.MongoTemplate.findAll(MongoTemplate.java:1064)
      at com.recorder.TestRecorder2.testObjectContainer(RecorderTest2.java:63)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:601)
      at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
      at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
      at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
      at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
      at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
      at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
      at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
      at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
      at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
      at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
      at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
      at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
      at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
      at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
      at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
  Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [com.recorder.TestRecorder2$ObjectContainer]: Illegal arguments for constructor; nested exception is java.lang.IllegalArgumentException: argument type mismatch
      at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:158)
      at org.springframework.data.convert.ReflectionEntityInstantiator.createInstance(ReflectionEntityInstantiator.java:75)
      ... 34 more
  Caused by: java.lang.IllegalArgumentException: argument type mismatch
      at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
      at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
      at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
      at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:147)
      ... 35 more
  </code></pre>
  
  <p>My <code>PrimitiveContainer</code> and <code>ObjectContainer</code> classes are listed below:</p>
  
  <pre><code>@Document
  class PrimitiveContainer {
  
      @Field("property") 
      private final int m_property;
  
      @PersistenceConstructor
      public PrimitiveContainer(@Value("#root.property") int a_property) {
          m_property = a_property;
      }
  
      public int property() {
          return m_property;
      }
  }
  
  @Document
  class ObjectContainer {
  
      @Field("property") 
      private final PrimitiveContainer m_property;
  
      @PersistenceConstructor
      public ObjectContainer(@Value("#root.property") PrimitiveContainer a_property) {
          m_property = a_property;
      }
  
      public PrimitiveContainer property() {
          return m_property;
      }
  }
  </code></pre>
  
  <hr>
  
  <p>**UPDATE: ** Curiously, changing the string in the <code>@Field</code> annotation to something other than "property" or removing the <code>@Field</code> annotation entirely for the <code>ObjectContainer</code> <code>m_property</code> allows spring-data-mongo-db to property re-instantiate my persisted <code>ObjectContainer</code> class.  I don't understand why this works. Anyone have any ideas?</p>