[英]How to deserialize array into an object?
我想要投射的对象看起来像
public class AdDimension {
private int width;
private int height;
public AdDimension() {
// needed by Jackson
}
public AdDimension(final int width, final int height) {
this.width = width;
this.height = height;
}
..
}
它用在里面
public class Campaign {
private String id;
private List<AdDimension> adDimensions;
public Campaign() {
// needed by Jackson
}
...
}
我尝试在测试中反序列化为
@Test
public void testLoadCampaigns() throws IOException {
final File campaignsFile = new File(getClass().getClassLoader().getResource("campaigns.json").getFile());
final List<Campaign> campaigns = new JsonReader().loadCampaigns(campaignsFile);
System.out.println(campaigns);
}
我的广告系列文件看起来像
[
{
"id": 1,
"targetedCountries": ["CA", "IT"],
"targetedDomain": "apple.com",
"adDimensions": [[300,250], [600,200]]
}
]
当我运行测试时,我看到
com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of com.org.site.messages.AdDimension out of START_ARRAY token
at [Source: /Users/harit/IdeaProjects/site/target/test-classes/campaigns.json; line: 6, column: 22] (through reference chain: java.util.ArrayList[0]->com.org.scout.messages.Campaign["adDimensions"]->java.util.ArrayList[0])
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:148)
at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:857)
at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:853)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromArray(BeanDeserializerBase.java:1257)
at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:157)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:136)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:245)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:217)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:25)
at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:520)
at com.fasterxml.jackson.databind.deser.impl.FieldProperty.deserializeAndSet(FieldProperty.java:101)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:258)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:125)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:245)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:217)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:25)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3736)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2639)
at com.org.harness.JsonReader.loadCampaigns(JsonReader.java:15)
at com.org.harness.JsonReaderTest.testLoadCampaigns(JsonReaderTest.java:17)
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:497)
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.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$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:252)
at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:141)
at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:112)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:189)
at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:165)
at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:85)
at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:115)
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:75)
Results :
Tests in error:
testLoadCampaigns(com.org.harness.JsonReaderTest): Can not deserialize instance of com.org.site.messages.AdDimension out of START_ARRAY token(..)
如何将[[300,250], [600,200]]
读入List<AdDimension>
?
默认情况下,Jackson尝试将JSON数组值反序列化为Java数组类型或Collection
类型(例如ArrayList
)。 但是,您正在尝试使其像[600,200]
这样的JSON数组反序列化为AdDimension
对象。 开箱即用。
您可以像建议其他答案一样更改JSON,也可以使用自定义反序列化策略。
您的第一个选择是定义一个自定义JsonDeserializer
(尽管您应该使用其sublcass StdDeserializer
)
class AdDimensionDeserializer extends JsonDeserializer<AdDimension> {
@Override
public AdDimension deserialize(JsonParser parser, DeserializationContext ctxt) throws IOException, JsonProcessingException {
// you have complete control over the tokens in the JSON, so validate as you wish
ArrayNode arrayNode = parser.readValueAsTree();
return new AdDimension(arrayNode.get(0).asInt(), arrayNode.get(1).asInt());
}
}
并注册为
@JsonDeserialize(using = AdDimensionDeserializer.class)
class AdDimension {
杰克逊将实例AdDimensionDeserializer
并使用实例的JSON数组元素反序列化为的一个实例(多个) AdDimension
。
另一种选择是使用@JsonCreater
标记批注,可用于将构造函数和工厂方法定义为用于实例化关联类的新实例的标记。
例如
@JsonCreator
public AdDimension(int[] dimensions) {
// again, validate as required
this.width = dimensions[0];
this.height = dimensions[1];
}
Jackson将找到此构造函数并将其用于反序列化JSON。 它将首先尝试将文本[300,250]
反序列化为显然可以的int[]
,然后将其传递给构造函数。
也许是错误的json格式?
我认为应该是这样
[
{
"id": 1,
"targetedCountries": ["CA", "IT"],
"targetedDomain": "apple.com",
"adDimensions": [{"width":300, "height":250}, {"width":600, "height":200}]
}
]
我现在无法对其进行测试,但这似乎不行。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.