引起原因：com.mongodb.MongoWriteException：E11000重复键错误集合：Blog.Posts索引：id dup键：{：null}

时间：2019-02-28 11:45:05

标签： mongodb mongodb-java spring-mongodb

我尝试使用Spring Boot将初始json文档加载到mongodb数据库中。首先，这些是mongodb文档架构。

@Document(collection="Posts") 
public class Post {

    @Id
    private String _id;

    @Indexed(unique = true) 
    private Long id; // This field is used for compatibility with Jpa Service interface

    private String title;

    private String body;

    private Date createdDate;

    @DBRef 
    private User user;

    @DBRef 
    private Collection<Tag> tags;
}

以下代码是初始json文件的内容。

[ {
    "Post" : {
        "id" : 1,
        "title" : "Title 1",
        "created_date" : "2018-12-01 11:10:13.247",
        "body" : " 국회는 헌법 또는 ....",
        "user" : {
            "username" : "joseph",
            "password" : "password"
        },
        "tags" : {
            "tag" : [
                {
                    "id" : 1,
                    "created_Date" : "2018-12-02 11:10:13.247",
                    "body" : "첫 글의 댓글입니다.",
                    "user" : {
                        "username" : "jina",
                        "password" : "password"
                    }
                },{
                    "id" : 2,
                    "created_Date" : "2018-12-03 11:10:13.247",
            "body" : "첫 글의 두번째 댓글입니다.",
            "user" : {
                        "username" : "julian",
                        "password" : "password"
                    } } ] } }   
}
,
{
    "post" : {
        "id" : 2,
        "title" : "Title 2",
        "created_date" : "2018-12-03 11:10:13.247",
        "body" : "제안된 헌법개정안은 대통령이 ....",
        "user" : {
            "username" : "joseph",
            "password" : "password"
        },
        "tags" : {
            "tag" : [
                {
                    "id" : 1,
                    "created_Date" : "2018-12-02 11:10:13.247",
                    "body" : "댓글 입니다.",
                    "user" : {
                        "username" : "julian",
                        "password" : "password"
                    } } ] } }   
}]

最后一部分是将上述初始json文件加载到mongodb中的函数。

@Override
    public void loadInitDocuments(String file) {
        // TODO Auto-generated method stub
        try (BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file), "EUC-KR"))) {
            String line;
            StringBuffer strBuffer = new StringBuffer();
            while ((line = br.readLine()) != null) {
                strBuffer.append(line+ "\n");
            }

            ObjectMapper objectMapper = new ObjectMapper();
            objectMapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
            TypeReference<List<Post>> typeReference = new TypeReference<List<Post>>(){};
            Collection<Post> posts = objectMapper.readValue(strBuffer.toString(), typeReference);
            System.out.println(posts.stream().collect(Collectors.toList()));

            if(postMongoRepository.count() == 0) {
                for(Post post : posts) {
                    postMongoRepository.save(post); // this line throws exception
                }
            }

            br.close();
        } catch (IOException ex) {
            System.out.println(ex.getMessage());
        }

但是MongoRepository.save行会引发异常。

Caused by: com.mongodb.MongoWriteException: E11000 duplicate key error collection: Blog.Posts index: id dup key: { : null }
    at com.mongodb.client.internal.MongoCollectionImpl.executeSingleWriteRequest(MongoCollectionImpl.java:967)
    at com.mongodb.client.internal.MongoCollectionImpl.executeInsertOne(MongoCollectionImpl.java:494)
    at com.mongodb.client.internal.MongoCollectionImpl.insertOne(MongoCollectionImpl.java:478)
    at com.mongodb.client.internal.MongoCollectionImpl.insertOne(MongoCollectionImpl.java:472)
    at org.springframework.data.mongodb.core.MongoTemplate$6.doInCollection(MongoTemplate.java:1436)
    at org.springframework.data.mongodb.core.MongoTemplate.execute(MongoTemplate.java:538)

我找到了使用谷歌搜索的原因。原因是“如果文档在唯一索引中没有索引字段的值，那么索引将为此文档存储一个空值。由于存在唯一性约束，MongoDB将只允许一个缺少索引字段的文档。 ”但是我不知道json文件的哪一部分值有误。

编辑部分

这次，我遇到@Dbref注释部分的问题。以下是用户文档代码，

@Document //
public class User {

    @Id //(2)
    private String _id;

    @Indexed(unique = true)
    private Long id;

    @Indexed(unique=true)
    private String username;

    private String password;
}

下面是修改后的初始json文件内容。

[
    {
        "id" : 0,
        "title" : "Title 1",
        "created_date" : "2018-12-01 11:10:13.247",
        "body" : " 국회는 헌법 또는 법률에 ",
        "user" : {
            "id" : 0,
            "username" : "joseph",
            "password" : "password"
        },
        "tag" : [
            {
                "id" : 0,
                "created_Date" : "2018-12-02 11:10:13.247",
                "body" : "첫 글의 댓글입니다.",
                "user" : {
                    "id" : 1,
                    "username" : "jina",
                    "password" : "password"
                }
            },{
                "id" : 1,
                "created_Date" : "2018-12-03 11:10:13.247",
          "body" : "첫 글의 두번째 댓글입니다.",
          "user" : {
                "id" : 2,
                  "username" : "julian",
                  "password" : "password"
                }
            } ] }

,
  {
        "id" : 1,
        "title" : "Title 2",
        "created_date" : "2018-12-03 11:10:13.247",
        "body" : "제안된 헌법개정안은 대통령이 20",
        "user" : {
            "id" : 0,
            "username" : "joseph",
            "password" : "password"
        },
        "tag" : [
            {
                "id" : 0,
                "created_Date" : "2018-12-02 11:10:13.247",
                "body" : "댓글 입니다.",
                "user" : {
                    "id" : 2,
                    "username" : "julian",
                    "password" : "password"
                } } ] } 
]

但是user文档未与json文件绑定。例外是... 

Cannot create a reference to an object with a NULL id.
org.springframework.data.mapping.MappingException: Cannot create a reference to an object with a NULL id.
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.createDBRef(MappingMongoConverter.java:975)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writePropertyInternal(MappingMongoConverter.java:597)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeAssociation(MappingMongoConverter.java:560)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeProperties(MappingMongoConverter.java:537)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeInternal(MappingMongoConverter.java:524)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeInternal(MappingMongoConverter.java:497)
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.write(MappingMongoConverter.java:441)

User文档未与Post文档绑定，因此返回空值。执行此行后，它返回false 

for(Post post : posts) {
  if(post.getUser().getId() == null)
    System.out.println("YES!! It is null");

  postMongoRepository.save(post);
}

1 个答案:

答案 0 :(得分：2)

在您的初始json文件中，您有2个文档组成的数组，这些文档只有一个根字段：第一个是“ Post”，第二个是“ post”。因此，保存第一个文档将导致id = null（因为定义了Post.id，但没有id）。而且与第二个一样会抛出错误... 尝试替换为，它必须可以工作... 

[ {
        "id" : 1,
        "title" : "Title 1",
        "created_date" : "2018-12-01 11:10:13.247",
        "body" : " 국회는 헌법 또는 ....",
        "user" : {
            "username" : "joseph",
            "password" : "password"
        },
        "tags" : {
            "tag" : [
                {
                    "id" : 1,
                    "created_Date" : "2018-12-02 11:10:13.247",
                    "body" : "첫 글의 댓글입니다.",
                    "user" : {
                        "username" : "jina",
                        "password" : "password"
                    }
                },{
                    "id" : 2,
                    "created_Date" : "2018-12-03 11:10:13.247",
            "body" : "첫 글의 두번째 댓글입니다.",
            "user" : {
                        "username" : "julian",
                        "password" : "password"
                    } } ] }   
}
,
{

        "id" : 2,
        "title" : "Title 2",
        "created_date" : "2018-12-03 11:10:13.247",
        "body" : "제안된 헌법개정안은 대통령이 ....",
        "user" : {
            "username" : "joseph",
            "password" : "password"
        },
        "tags" : {
            "tag" : [
                {
                    "id" : 1,
                    "created_Date" : "2018-12-02 11:10:13.247",
                    "body" : "댓글 입니다.",
                    "user" : {
                        "username" : "julian",
                        "password" : "password"
                    } } ] }    
}]
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