Java操作MongoDB：利用唯一索引高效处理文档重复插入

db.yourCollectionName.createIndex(
   {
     "name": 1,
     "supplier": 1,
     "food": 1,
     "country of origin": 1
   },
   { unique: true }
)

import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;
import com.mongodb.client.model.IndexOptions;
import com.mongodb.client.model.Indexes;
import com.mongodb.MongoCommandException;

// 假设 mongoClient 是已连接的MongoClient实例
// MongoDatabase database = mongoClient.getDatabase("yourDatabaseName");
MongoCollection<Document> collection = database.getCollection("yourCollectionName");

// 定义构成唯一键的字段及其排序方式
Document uniqueKeys = new Document()
    .append("name", 1)
    .append("supplier", 1)
    .append("food", 1)
    .append("country of origin", 1);

// 设置索引选项，指定为唯一索引
IndexOptions indexOptions = new IndexOptions().unique(true);

try {
    // 创建唯一索引。如果索引已存在，MongoDB通常会忽略创建请求，除非选项不同。
    String indexName = collection.createIndex(uniqueKeys, indexOptions);
    System.out.println("成功创建唯一索引: " + indexName);
} catch (MongoCommandException e) {
    // 错误代码 48 通常表示索引已存在且属性不同，或尝试创建不同属性的同名索引
    if (e.getErrorCode() == 48) {
        System.out.println("唯一索引已存在或尝试创建不同属性的同名索引: " + e.getMessage());
    } else {
        System.err.println("创建唯一索引时发生错误: " + e.getMessage());
    }
} catch (Exception e) {
    System.err.println("创建唯一索引时发生未知错误: " + e.getMessage());
}

import com.mongodb.MongoWriteException;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.result.InsertOneResult;
import org.bson.Document;

// 假设 collection 是已获取的MongoCollection<Document>实例
// MongoCollection<Document> collection = ...;

Document newDocument = new Document();
newDocument.put("name", "Apple");
newDocument.put("supplier", "Fruit Inc.");
newDocument.put("food", "Fruit");
newDocument.put("country of origin", "USA");

try {
    InsertOneResult result = collection.insertOne(newDocument);
    if (result.wasAcknowledged()) {
        System.out.println("文档插入成功，_id: " + result.getInsertedId());
    }
} catch (MongoWriteException e) {
    // 检查是否是重复键错误 (错误代码 11000)
    if (e.getError().getCode() == 11000) {
        System.err.println("[错误] 尝试插入重复文档: " + newDocument.toJson());
        // 根据业务需求，可以选择抛出自定义异常或记录日志
        // throw new CustomDuplicateDocumentException("Document already exists.", e);
    } else {
        System.err.println("插入文档时发生其他写入错误: " + e.getMessage());
    }
} catch (Exception e) {
    System.err.println("插入文档时发生未知错误: " + e.getMessage());
}

import com.mongodb.client.MongoCollection;
import com.mongodb.client.model.Filters;
import org.bson.Document;
import org.bson.conversions.Bson;
import com.mongodb.client.result.InsertOneResult;

// 假设 collection 是已获取的MongoCollection<Document>实例
// MongoCollection<Document> collection = ...;

String name = "Apple";
String supplier = "Fruit Inc.";
String food = "Fruit";
String countryOfOrigin = "USA";

// 构建查询过滤器，用于查找是否存在匹配的文档
Bson filter = Filters.and(
        Filters.eq("name", name),
        Filters.eq("supplier", supplier),
        Filters.eq("food", food),
        Filters.eq("country of origin", countryOfOrigin)
);

// 执行查找操作，获取第一个匹配的文档
Document existingDocument = collection.find(filter).first();

if (existingDocument == null) {
    // 未找到重复文档，可以安全插入
    Document documentToInsert = new Document()
        .append("name", name)
        .append("supplier", supplier)
        .append("food", food)
        .append("country of origin", countryOfOrigin);

    try {
        InsertOneResult result = collection.insertOne(documentToInsert);
        if (result.wasAcknowledged()) {
            System.out.println("文档插入成功，_id: " + result.getInsertedId());
        }
    } catch (Exception e) {
        System.err.println("插入文档时发生错误: " + e.getMessage());
    }
} else {
    System.out.println("已存在重复文档，无需插入: " + existingDocument.toJson());
    // 根据业务需求，可以抛出异常或执行其他逻辑
    // throw new RuntimeException("[Error] duplicate insertion detected before insert attempt");
}