我正在尝试编写使用Jackson将对象序列化/反序列化为File的代码。
对象本质上是多态的。我的界面看起来像
@JsonIgnoreProperties(ignoreUnknown = true)
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY)
@JsonSubTypes({
@JsonSubTypes.Type(RemoteDataSource.class),
@JsonSubTypes.Type(FileDataSource.class)
})
public interface DataSource {
}
和实现
public class FileDataSource implements DataSource {
private String path;
private String delimiter;
private String fileNamePattern;
@JsonCreator
public FileDataSource(@JsonProperty("path") String path,
@JsonProperty("delimiter") String delimiter,
@JsonProperty("fileNamePattern") String fileNamePattern) {
this.path = path;
this.delimiter = delimiter;
this.fileNamePattern = fileNamePattern;
}
...
}
和
public class RemoteDataSource implements DataSource {
private String host;
private int port;
private String userName;
private String password;
@JsonCreator
public RemoteDataSource(@JsonProperty("host") String host,
@JsonProperty("port") int port,
@JsonProperty("userName") String userName,
@JsonProperty("password") String password) {
this.host = host;
this.port = port;
this.userName = userName;
this.password = password;
}
...
}
并在WorkflowConfig中使用
public class WorkflowConfig {
private String name;
private DataSource dataSource;
@JsonCreator
public WorkflowConfig(@JsonProperty("name") String name,
@JsonProperty("dataSource") DataSource dataSource) {
this.name = name;
this.dataSource = dataSource;
}
...
}
然后我写了我的测试，看起来像
@Test
public void testSerializeAndSerializeFileDataSourceFromFile() throws Exception {
File fileDataSource = temporaryFolder.newFile("fileDataSource.json");
DataSource dataSource = new FileDataSource("/tmp/", ",", ".*");
WorkflowConfig config = new WorkflowConfig("fileWorkflowConfig", dataSource);
ObjectMapper mapper = new ObjectMapper();
mapper.writeValue(fileDataSource, config);
assertTrue(fileDataSource.length() > 0);
DataSource readDataSource = mapper.readValue(fileDataSource, DataSource.class);
assertNotNull(readDataSource);
}
，它失败了
com.fasterxml.jackson.databind.JsonMappingException: Unexpected token (END_OBJECT), expected FIELD_NAME: missing property '@type' that is to contain type id (for class com.datasources.DataSource)
at [Source: /var/folders/g3/wtbqfj7d5fsbkz1gm74kqy380000gn/T/junit5577276768876379004/fileDataSource.json; line: 1, column: 123]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:261)
at com.fasterxml.jackson.databind.DeserializationContext.wrongTokenException(DeserializationContext.java:1340)
at com.fasterxml.jackson.databind.DeserializationContext.reportWrongTokenException(DeserializationContext.java:1196)
at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer._deserializeTypedUsingDefaultImpl(AsPropertyTypeDeserializer.java:157)
at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer.deserializeTypedFromObject(AsPropertyTypeDeserializer.java:105)
at com.fasterxml.jackson.databind.deser.AbstractDeserializer.deserializeWithType(AbstractDeserializer.java:142)
at com.fasterxml.jackson.databind.deser.impl.TypeWrappedDeserializer.deserialize(TypeWrappedDeserializer.java:42)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3789)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2731)
at com.workflow.WorkflowConfigTest.testSerializeAndSerializeFileDataSourceFromFile(WorkflowConfigTest.java:55)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.rules.ExternalResource$1.evaluate(ExternalResource.java:48)
at org.junit.rules.RunRules.evaluate(RunRules.java:20)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
序列化时，文件中的数据类似于
{"name":"fileWorkflowConfig","dataSource":{"@type":"FileDataSource","path":"/tmp/","delimiter":",","fileNamePattern":".*"}}
我相信Jackson需要@type信息来构建正确的对象。
但从应用程序的角度来看，我不需要这些信息，所以我使用了
@JsonIgnoreProperties(ignoreUnknown = true)
但是我相信我犯了错误，我现在该怎么办？
完整的代码库位于GitHub。你可以在那里看到失败的测试
答案 0 :(得分：2)
测试有错误，您正在序列化WorkflowConfig但尝试直接反序列化DataSource。
测试反序列化应该是：
WorkflowConfig workflowConfig= mapper.readValue(fileDataSource, WorkflowConfig.class);
assertNotNull(workflowConfig);
assertNotNull(workflowConfig.getDataSource());