为什么Spring Data MongoDB无法实例化此嵌套类型结构? [英] Why is Spring Data MongoDB unable to instantiate this nested type structure?

问题描述

我的文档结构如下:

{
    _id: "A",
    groups:[{
        groupId: "someId",
        groupName: "someName",
        params: {
            type1: ["a", "b"],
            type2: ["c", d]
        }
    }],
    config: {
        person: {}
        dataDetails: {
            dataTypeDetails: {},
            dataList: ["dt1", "dt2"]
        }
    }
}

我的Spring Data MongoDB模型类型如下:

My Spring Data MongoDB model types look like this:

// Imports etc.
@Document
public class Entity {

    @Id
    private String _id;

    private List<Group> groups;
    private Config config;
    // setters and getters

    public class Group {
        private String groupId;
        private String groupName;
        private ParamData params;

        // setter and getters
    }

    public class ParamData {
        private List<String> type1;
        private List<String> type2;
    }

    public class Config {
        private Map person;
        private DataConfig dataDetails;
    }

    public class DataConfig {
        private Map dataTypeDetails;
        private List<String> dataList;
    }
}

Stacktrace:

Stacktrace:

org.springframework.data.mapping.model.MappingInstantiationException: Failed to instantiate com.****.common.models.Entity$ParamData using constructor public com.****.common.models.Entity$ParamData(com.****.common.models.Entity) with arguments com.****.common.models.Entity$Group@2eb61a7b
    at org.springframework.data.convert.ReflectionEntityInstantiator.createInstance(ReflectionEntityInstantiator.java:78)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:257)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:237)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readValue(MappingMongoConverter.java:1136)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.access$100(MappingMongoConverter.java:78)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$MongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1085)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.getValueInternal(MappingMongoConverter.java:816)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$1.doWithPersistentProperty(MappingMongoConverter.java:270)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$1.doWithPersistentProperty(MappingMongoConverter.java:263)
    at org.springframework.data.mapping.model.BasicPersistentEntity.doWithProperties(BasicPersistentEntity.java:261)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:263)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:237)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readCollectionOrArray(MappingMongoConverter.java:861)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readValue(MappingMongoConverter.java:1134)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.access$100(MappingMongoConverter.java:78)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$MongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1085)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.getValueInternal(MappingMongoConverter.java:816)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$1.doWithPersistentProperty(MappingMongoConverter.java:270)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$1.doWithPersistentProperty(MappingMongoConverter.java:263)
    at org.springframework.data.mapping.model.BasicPersistentEntity.doWithProperties(BasicPersistentEntity.java:261)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:263)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:237)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:201)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:197)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:78)
    at org.springframework.data.mongodb.core.MongoTemplate$ReadDbObjectCallback.doWith(MongoTemplate.java:2016)
    at org.springframework.data.mongodb.core.MongoTemplate.executeFindMultiInternal(MongoTemplate.java:1700)
    at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:1523)
    at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:1507)
    at org.springframework.data.mongodb.core.MongoTemplate.find(MongoTemplate.java:532)
    at org.springframework.data.mongodb.core.MongoTemplate.findOne(MongoTemplate.java:497)
    at org.springframework.data.mongodb.core.MongoTemplate.findOne(MongoTemplate.java:489)

在DAO中，我试图通过标识符获取文档，但是仅对dataDetails和params中的值失败.如果注释掉ParamData参数，则会出现DataConfig的错误.数据是使用命令行/节点脚本添加的，而不是使用此代码添加的.但是，可以通过节点/猫鼬以及从命令行正确地检索到它.

My in DAO I am trying to fetch the document by identifier, but it is failing only for the values at dataDetails and params. If I comment out the ParamData param, I get error for DataConfig. The data was added using command line/node scripts and was not added using this code. But it is getting retrieved properly by node/mongoose as well as from command line.

推荐答案

这似乎是双重嵌套内部类和由编译器创建的合成生成的构造函数的问题.我可以在本地重现该问题，看看是否可以提供解决方案.同时，您有两种选择:

This seems to be an issue with doubly nested inner classes and the synthetically generated constructors created by the compiler. I could reproduce that issue locally and see if we can provide a fix. In the meantime you have two options:

1. 将内部类转换为静态类，因为这将删除综合构造函数，并且实例化将正常工作.
2. 嵌套类型声明的方式与嵌套属性的方式相同. IE.将ParamData类移到Group类中，将DataConfig移到Config中，因为这将导致以与Spring Data当前依赖的实例化顺序匹配的方式创建综合构造函数.

1. Turn the inner class into static ones as this will remove the synthetic constructors and instantiation will work correctly.
2. Nest the type declarations in the same way you nest the properties. I.e. move the ParamData class into the Group class, DataConfig into Config as that will cause the synthetic constructors created in a way they match instantiation order Spring Data currently relies on.

我建议采用前一种方法，因为它不会人为地将类绑定到外部类的实例.

I'd suggest the former approach as it doesn't artificially bind the classes to instances of the outer class.

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