MappedFieldsTracker throws Exceptions

[xiaoxiaoxing]

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• For issues or feature requests related to the code in this repository file a Github issue.
• For general technical questions, post a question on Google Groups.

Whats your runtime?

• Dozer version: 6.5.1
• OS version: _____
• JDK version: 8

Whats the problem?

I am trying to upgrade DozerMapper from5.4 to 6.x, I started to see spike of Exceptions from DozerMapper when deployed the change to production environment. I could not reproduce the issue in our gamma environment by manually triggering some requests. I am not familiar with the DozerMapper implemention, I am wondering do you have any idea what could happen here? Thanks.

There are two types of Exceptions:

1. java.lang.IllegalStateException: No transaction with ID 0
2. java.lang.NullPointerException: null

Looks like the "No transaction with ID" exception was thrown from pendingTransactions in MappedFieldsTracker, is MappedFieldsTracker a singleton? Is it supposed to be thread safe?

I pasted parts of the logs here:
java.lang.IllegalStateException: No transaction with ID 0 at com.github.dozermapper.core.MappedFieldsTracker.commitTransaction(MappedFieldsTracker.java:99) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.addOrUpdateToList(MappingProcessor.java:901) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.addOrUpdateToList(MappingProcessor.java:961) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapListToList(MappingProcessor.java:791) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapCollection(MappingProcessor.java:641) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapOrRecurseObject(MappingProcessor.java:500) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapFromFieldMap(MappingProcessor.java:404) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapField(MappingProcessor.java:354) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.map(MappingProcessor.java:314) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapToDestObject(MappingProcessor.java:263) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.createByCreationDirectiveAndMap(MappingProcessor.java:236) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapGeneral(MappingProcessor.java:209) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.map(MappingProcessor.java:132) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.map(MappingProcessor.java:127) ~[dozer-core-6.5.1.jar:?] at xxxCustomConverter.convert(xxxCustomConverter.java:40) ~[xxxService-1.0.jar:?]

java.lang.NullPointerException: null at com.github.dozermapper.core.MappedFieldsTracker.put(MappedFieldsTracker.java:155) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.map(MappingProcessor.java:273) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapToDestObject(MappingProcessor.java:263) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.createByCreationDirectiveAndMap(MappingProcessor.java:236) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapCustomObject(MappingProcessor.java:575) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapOrRecurseObject(MappingProcessor.java:512) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.addOrUpdateToList(MappingProcessor.java:885) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.addOrUpdateToList(MappingProcessor.java:961) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapListToList(MappingProcessor.java:791) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapCollection(MappingProcessor.java:641) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapOrRecurseObject(MappingProcessor.java:500) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapFromFieldMap(MappingProcessor.java:404) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapField(MappingProcessor.java:354) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.map(MappingProcessor.java:314) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapToDestObject(MappingProcessor.java:263) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.createByCreationDirectiveAndMap(MappingProcessor.java:236) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.mapGeneral(MappingProcessor.java:209) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.map(MappingProcessor.java:132) ~[dozer-core-6.5.1.jar:?] at com.github.dozermapper.core.MappingProcessor.map(MappingProcessor.java:127) ~[dozer-core-6.5.1.jar:?] at xxxCustomConverter.convert(xxxCustomConverter.java:40) ~[xxxService-1.0.jar:?]

Observed Results:

Exceptions from DozerMapper.

Expected Results:

No Exception from DozerMapper.

Link to GitHub repo with Unit test

NA

[garethahealy]

@xiaoxiaoxing ; no, sorry. but looking at the stack, this is the only PR affecting MappedFieldsTracker

• be17136#diff-a68dd9947ad647a31594dd9c3ac8afe8d64fdbcdcea3a6dc695a51ff18e2b4e0

which was released in 6.5.0:

• https://github.com/DozerMapper/dozer/releases

can you try 6.4.1?

[xiaoxiaoxing]

Hi, @garethahealy:
Thanks for you reply!

Yes, I agree with you, I believe the issue is caused by the new transaction feature introduced in 6.5.0, looks like in multi-threads environment, the state of pendingTransactions in MappedFieldsTracker could be messed up.

I am able to reproduce the issue by unit test, and when I downgrade to 6.4.0, the issue is gone.

Here is my unit test:

public class ClassA {
    private String field1;
    private Long field2;
    private Map<String, String> field3;
    private Map<String, ClassB> field4;

    public String getField1() {
        return field1;
    }

    public void setField1(String field1) {
        this.field1 = field1;
    }

    public Long getField2() {
        return field2;
    }

    public void setField2(Long field2) {
        this.field2 = field2;
    }

    public Map<String, String> getField3() {
        return field3;
    }

    public void setField3(Map<String, String> field3) {
        this.field3 = field3;
    }

    public Map<String, ClassB> getField4() {
        return field4;
    }

    public void setField4(Map<String, ClassB> field4) {
        this.field4 = field4;
    }
}

public class ClassB {
    private String field1;
    private Long field2 ;
    private List<ClassC> field3;

    public String getField1() {
        return field1;
    }

    public void setField1(String field1) {
        this.field1 = field1;
    }

    public Long getField2() {
        return field2;
    }

    public void setField2(Long field2) {
        this.field2 = field2;
    }

    public List<ClassC> getField3() {
        return field3;
    }

    public void setField3(final List<ClassC> field3) {
        this.field3 = field3;
    }
}

public class ClassC {
    private String field1;
    private Long field2;

    public String getField1() {
        return field1;
    }

    public void setField1(String field1) {
        this.field1 = field1;
    }

    public Long getField2() {
        return field2;
    }

    public void setField2(Long field2) {
        this.field2 = field2;
    }
}

public class ClassAA {
    private String field1;
    private Long field2;
    private Map<String, String> field3;
    private List<ClassBB> field4;

    public String getField1() {
        return field1;
    }

    public void setField1(String field1) {
        this.field1 = field1;
    }

    public Long getField2() {
        return field2;
    }

    public void setField2(Long field2) {
        this.field2 = field2;
    }

    public Map<String, String> getField3() {
        return field3;
    }

    public void setField3(Map<String, String> field3) {
        this.field3 = field3;
    }

    public List<ClassBB> getField4() {
        return field4;
    }

    public void setField4(List<ClassBB> field4) {
        this.field4 = field4;
    }
}

public class ClassBB {
    private String field1;
    private Long field2 ;
    private List<ClassCC> field3;

    public String getField1() {
        return field1;
    }

    public void setField1(String field1) {
        this.field1 = field1;
    }

    public Long getField2() {
        return field2;
    }

    public void setField2(Long field2) {
        this.field2 = field2;
    }

    public List<ClassCC> getField3() {
        return field3;
    }

    public void setField3(final List<ClassCC> field3) {
        this.field3 = field3;
    }
}

public class ClassCC {
    private String field1;
    private Long field2;

    public String getField1() {
        return field1;
    }

    public void setField1(String field1) {
        this.field1 = field1;
    }

    public Long getField2() {
        return field2;
    }

    public void setField2(Long field2) {
        this.field2 = field2;
    }
}

public class MyCustomConverter implements CustomConverter, MapperAware {
    private Mapper mapper;

    @SuppressWarnings("unchecked")
    @Override
    @Nullable
    public Object convert(
        @Nullable Object destination,
        @Nullable Object source,
        @Nonnull Class<?> destClass,
        @Nonnull Class<?> sourceClass) {

        if (source == null) {
            return null;
        }

        if (source instanceof Map) {
            Map<String, ClassB> inputMap = (Map<String, ClassB>)source;
            List<ClassBB> convertedValues = new ArrayList<>();
            for (Map.Entry<String, ClassB> entry : inputMap.entrySet()) {
                ClassBB classBB = mapper.map(entry.getValue(), ClassBB.class);
                convertedValues.add(classBB);
            }

            return convertedValues;
        } else {
            throw new MappingException("Converter MarketplaceSubscriptionDetailsCustomConverter "
                + "used incorrectly. Arguments passed in were:"
                + destination + " and " + source);
        }
    }

    @Override
    public void setMapper(Mapper mapper) {
        this.mapper = mapper;
    }
}

<bean id="myCustomConverter"
          class="com.amazon.prise.dao.dto.converters.MyCustomConverter"/>

<bean id="dozerBeanMapperBuilderWithMappingFilesAndCustomConvertersWithId" class="com.github.dozermapper.core.DozerBeanMapperBuilder" factory-bean="dozerBeanMapperBuilderWithMappingFiles" factory-method="withCustomConvertersWithIds">
        <constructor-arg name="customConvertersWithId">
            <map>
                <entry key="myCustomConverter" value-ref="myCustomConverter" />
            </map>
        </constructor-arg>
</bean>

<mapping type="one-way">
        <class-a>com.amazon.prise.activity.ClassA</class-a>
        <class-b>com.amazon.prise.activity.ClassAA</class-b>

        <field custom-converter-id="myCustomConverter">
            <a>field4</a>
            <b>field4</b>
        </field>
</mapping>

private ClassA createInput_concurrency(String str, long l) {
        ClassC classC = new ClassC();
        classC.setField1("Field1" + str);
        classC.setField2(123L + l);
        List<ClassC> classCList = new ArrayList<>();
        classCList.add(classC);

        ClassB classB = new ClassB();
        classB.setField1("Field1" + str);
        classB.setField2(123L + l);
        classB.setField3(classCList);
        Map<String, ClassB> classBMap = new HashMap<>();
        classBMap.put("Key" + str, classB);

        Map<String, String> map = new HashMap<>();
        map.put("K1" + str, "V1");
        map.put("K2" + str, "V2");
        map.put("K3" + str, "V3");

        ClassA classA = new ClassA();
        classA.setField1("Field1" + str);
        classA.setField2(123L + l);
        classA.setField3(map);
        classA.setField4(classBMap);

        return classA;
 }

@Test
public void convert_concurrency() {
        replayAll();

        int numOfThreads = 200;
        ExecutorService service = Executors.newFixedThreadPool(numOfThreads);
        for (int i = 0; i < numOfThreads; i++) {
            String string = String.valueOf(i);
            long l = i;
            service.execute(() -> {
                ClassA input = createInput_concurrency(string, l);
                Object output = dozerMapper.map(input, ClassAA.class);
            });
        }
 }

Run the above test for a couple times, you would see either IllegalStateException or NPE will be thrown from some of the threads in MappedFieldsTracker.