java - Dozer 无法映射 Collection 成员

Question

我有一个包含集合的对象:

public class Wrapper {
    private Collection<Base> bases = new LinkedList<Base>();
    public Collection<Base> getBases() {return bases;}
    public void setBases(final Collection<Base> bases) {this.bases = bases;}
}

接口(interface)的实现非常简单:

public class BaseOne implements Base {
}

public class BaseTwo implements Base {
}

当我运行一个简单的测试时:

@Test
public void testCopyOther() {
    final Wrapper wrapper =  new Wrapper();
    wrapper.getBases().add(new BaseOne());

    final Wrapper copy = dozer.map(wrapper, Wrapper.class);
}

我得到这个异常:

org.dozer.MappingException: java.lang.NoSuchMethodException: com.usamp.biddingtool.model.service.impl.Base.<init>()
    at org.dozer.util.MappingUtils.throwMappingException(MappingUtils.java:82)
    at org.dozer.factory.ConstructionStrategies$ByConstructor.newInstance(ConstructionStrategies.java:261)
    at org.dozer.factory.ConstructionStrategies$ByConstructor.create(ConstructionStrategies.java:245)
    at org.dozer.factory.DestBeanCreator.create(DestBeanCreator.java:65)
    at org.dozer.MappingProcessor.mapCustomObject(MappingProcessor.java:489)
    at org.dozer.MappingProcessor.mapOrRecurseObject(MappingProcessor.java:446)
    at org.dozer.MappingProcessor.addOrUpdateToList(MappingProcessor.java:776)
    at org.dozer.MappingProcessor.addOrUpdateToList(MappingProcessor.java:850)
    at org.dozer.MappingProcessor.mapListToList(MappingProcessor.java:686)
    at org.dozer.MappingProcessor.mapCollection(MappingProcessor.java:541)
    at org.dozer.MappingProcessor.mapOrRecurseObject(MappingProcessor.java:434)
    at org.dozer.MappingProcessor.mapFromFieldMap(MappingProcessor.java:342)
    at org.dozer.MappingProcessor.mapField(MappingProcessor.java:288)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:248)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:197)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:187)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:124)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:119)
    at org.dozer.DozerBeanMapper.map(DozerBeanMapper.java:120)
    at com.usamp.biddingtool.model.service.impl.DozerTest.testCopyOther(DozerTest.java:52)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:88)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:77)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:195)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:63)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

因此，Dozer 似乎正在尝试创建集合中使用的实际类型的实例，而该类型只是一个接口(interface)。由于接口(interface)无法实例化，因此会产生错误。

我看到其他人问过这个问题，但没有真正得到任何具体答案。这个问题有解决办法吗？

谢谢。-AP_

Answer 1

您必须向 Dozer 提供有关 Base 实现的提示。否则它将尝试实例化接口(interface)，但这是不可能的。
<mapping>
<class-a>Wrapper</class-a>
<class-b>Wrapper</class-b>
<field>
<a>bases</a>
<b>bases</b>
<a-hint>BaseOne,BaseTwo</a-hint>
<b-hint>BaseOne,BaseTwo</b-hint>
</field>
</mapping>

http://dozer.sourceforge.net/documentation/baseattributes.html

替代方案(更新):
<mapping>
<class-a>BaseOne</class-a>
<class-b>BaseOne</class-b>
</mapping>
<mapping>
<class-a>BaseTwo</class-a>
<class-b>BaseTwo</class-b>
</mapping>