mongodb java Driver 3.5.0 POJOs

本文介绍如何在不使用Spring-data-mongodb的情况下,通过POJO支持实现MongoDB的数据操作。主要内容包括配置Maven依赖、创建实体类、实现数据访问接口等,并解决了因实体类上的JPA注解引发的问题。

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项目采用模块化开发,无法在实体上使用注解,所以Spring-data-mongodb无法使用因为实体上加了JPA的@Entity注解导致MongoPersistentEntityIndexCreator找不到类,只能使用原生的api,有了pojo的支持不再需要繁琐的代码

pom.xml

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <mongodb.version>3.5.0</mongodb.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.mongodb</groupId>
            <artifactId>mongodb-driver</artifactId>
            <version>${mongodb.version}</version>
        </dependency>
        <dependency>
            <groupId>org.mongodb</groupId>
            <artifactId>mongo-java-driver</artifactId>
            <version>${mongodb.version}</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

实体类

/**
 * mongodb 主键对象
 * @author xiaofanku@live.cn
 * @since 20170912
 */
public class SequenceId {
    private String id;
    private long seq;
    //SET/GET
}
/**
 * 实体
 * @author xiaofanku@live.cn
 * @since 20170912
 */
public class ForumMemberOnline implements Serializable{
    private Long ID;
    private int memberId=0;
    private int uid=0;
    private String sessionId;
    private String nickname="guest";
    //SET/GET
}

接口实现

import com.mongodb.MongoClient;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import static com.mongodb.client.model.Filters.and;
import static com.mongodb.client.model.Filters.eq;
import static com.mongodb.client.model.Filters.gt;
import static com.mongodb.client.model.Filters.in;
import static com.mongodb.client.model.Updates.combine;
import static com.mongodb.client.model.Updates.inc;
import static com.mongodb.client.model.Updates.set;
import com.mongodb.client.result.DeleteResult;
import java.util.ArrayList;
import java.util.List;
import net.htage.querylab.entity.ForumMemberOnline;
import net.htage.querylab.helper.SequenceId;
import net.htage.querylab.service.ForumMemberOnlineService;
import org.bson.codecs.configuration.CodecProvider;
import org.bson.codecs.configuration.CodecRegistry;
import org.bson.codecs.pojo.PojoCodecProvider;
import static org.bson.codecs.configuration.CodecRegistries.fromProviders;
import static org.bson.codecs.configuration.CodecRegistries.fromRegistries;
/**
 * 接口实现
 * @author xiaofanku@live.cn
 * @since 20170912
 */
public class ForumMemberOnlineServiceImpl implements ForumMemberOnlineService{
    private final MongoCollection<ForumMemberOnline> collection;
    private final MongoDatabase database;
    private static final String IDKEY="hosting";

    public ForumMemberOnlineServiceImpl(){
        CodecProvider pojoCodecProvider = PojoCodecProvider.builder().automatic(true).build();
        CodecRegistry pojoCodecRegistry = fromRegistries(MongoClient.getDefaultCodecRegistry(), fromProviders(pojoCodecProvider));

        MongoClient mongoClient = new MongoClient("10.0.0.4", 27017);
        this.database = mongoClient.getDatabase("htage_ol").withCodecRegistry(pojoCodecRegistry);

        this.collection = database.getCollection("apo_forum_online", ForumMemberOnline.class);
    }

    @Override
    public boolean isOnline(int memberId) {
        try{
            ForumMemberOnline rs = collection.find(eq("memberId", memberId)).first();
            if(rs.getID()>0){
                return true;
            }
        }catch(Exception e){
            throw new NullPointerException();
        }
        return false;
    }

    @Override
    public boolean offline(String sessionId) {
        DeleteResult dr = collection.deleteOne(eq("sessionId", sessionId));
        return dr.getDeletedCount()==1;
    }

    @Override
    public ForumMemberOnline get(String sessionId) {
        return collection.find(eq("sessionId", sessionId)).first();
    }

    @Override
    public ForumMemberOnline save(ForumMemberOnline entity) {
        try{
            if(entity.getID()==null){
                entity.setID(getNextSequenceId());
            }
        }catch(NullPointerException e){
            return null;
        }
        collection.insertOne(entity);
        return entity;
    }

    @Override
    public ForumMemberOnline findOne(Long primaryKey) {
        return collection.find(eq("iD", primaryKey)).first();
    }

    @Override
    public void edit(ForumMemberOnline entity) {
        collection.updateOne(
                eq("sessionId", entity.getSessionId()), 
                combine(
                        set("memberId", entity.getMemberId()), 
                        set("uid", entity.getUid()), 
                        set("nickname", entity.getNickname())));
    }

    @Override
    public Long count() {
        return collection.count();
    }

    @Override
    public List<ForumMemberOnline> findAll() {
        return collection.find().into(new ArrayList<>());
    }

    @Override
    public List<ForumMemberOnline> isOnline(List<Integer> uids) {
        return collection.find(and(gt("memberId", 0), in("uid", uids))).into(new ArrayList<>());
    }

    private long getNextSequenceId() throws NullPointerException {
        //BasicDBObject find = new BasicDBObject();
        //find.put("_id", IDKEY);

        //BasicDBObject update = new BasicDBObject();
        //update.put("$inc", new BasicDBObject("seq", 1));
        MongoCollection<SequenceId> coll = database.getCollection("sequence", SequenceId.class);

        SequenceId seqId = coll.findOneAndUpdate(eq("_id", IDKEY), inc("seq", 1));
        if (seqId == null) {
            throw new NullPointerException("Unable to get sequence id for key : " + IDKEY);
        }
        return seqId.getSeq();
    }
}

如果实体上有其它注解
例如:如果实体上有javax.persistence.Entity注解,可能会有以下异常栈

org.bson.codecs.configuration.CodecConfigurationException: Can't find a codec for class net.htage.forum.entity.ForumMemberOnline.
    at org.bson.codecs.configuration.CodecCache.getOrThrow(CodecCache.java:46)
    at org.bson.codecs.configuration.ProvidersCodecRegistry.get(ProvidersCodecRegistry.java:63)
    at org.bson.codecs.configuration.ProvidersCodecRegistry.get(ProvidersCodecRegistry.java:37)
    at com.mongodb.MongoCollectionImpl.getCodec(MongoCollectionImpl.java:591)
    at com.mongodb.MongoCollectionImpl.insertOne(MongoCollectionImpl.java:314)
    at com.mongodb.MongoCollectionImpl.insertOne(MongoCollectionImpl.java:307)
    ...

主要原因 是下面的代码没有将net.htage.forum.entity.ForumMemberOnline加入到CodecCache中

CodecProvider pojoCodecProvider = PojoCodecProvider.builder().automatic(true).build();

CodecCache.getOrThrow方法

   @SuppressWarnings("unchecked")
    public <T> Codec<T> getOrThrow(final Class<T> clazz) {
        if (codecCache.containsKey(clazz)) {
            Optional<? extends Codec<?>> optionalCodec = codecCache.get(clazz);
            if (!optionalCodec.isEmpty()) {
                return (Codec<T>) optionalCodec.get();
            }
        }
        throw new CodecConfigurationException(format("Can't find a codec for %s.", clazz));
    }

解决方案 自定义一个ForumMemberOnline的Codec

/**
 * ForumMemberOnline编码和解码
 * @author xiaofanku@live.cn
 * @since 20170913
 */
public class ForumMemberOnlineCodec implements Codec<ForumMemberOnline>{

    @Override
    public void encode(BsonWriter writer, ForumMemberOnline t, EncoderContext ec) {
        writer.writeStartDocument();
        writer.writeInt64("_id", t.getID());
        writer.writeInt32("uid", t.getUid());
        writer.writeInt32("memberId", t.getMemberId());
        writer.writeString("nickname", t.getNickname());
        writer.writeString("sessionId", t.getSessionId());
        writer.writeEndDocument();
    }

    @Override
    public Class<ForumMemberOnline> getEncoderClass() {
        return ForumMemberOnline.class;
    }

    @Override
    public ForumMemberOnline decode(BsonReader reader, DecoderContext dc) {
        ForumMemberOnline fmo=new ForumMemberOnline();
        reader.readStartDocument(); 
        fmo.setID(reader.readInt64("_id"));
        fmo.setUid(reader.readInt32("uid"));
        fmo.setMemberId(reader.readInt32("memberId"));
        fmo.setNickname(reader.readString("nickname"));
        fmo.setSessionId(reader.readString("sessionId"));
        reader.readEndDocument();
        return fmo;
    }

}

ForumMemberOnlineServiceImpl的构造函数稍作更改

    public ForumMemberOnlineDaoMongoImpl(){
        //自定义
        CodecRegistry customCodecRegistry = CodecRegistries.fromCodecs(new ForumMemberOnlineCodec(), new SequenceIdCodec());
        CodecRegistry combineCodecRegistry = fromRegistries(MongoClient.getDefaultCodecRegistry(), customCodecRegistry);

        MongoClient mongoClient = new MongoClient("10.0.0.4", 27017);
        this.database = mongoClient.getDatabase("htage_ol").withCodecRegistry(combineCodecRegistry);
        this.collection = database.getCollection("apo_forum_online", ForumMemberOnline.class);
    }

MongoClient.getDefaultCodecRegistry()是一些基础对象的编码和解码.

public class MongoClient extends Mongo implements Closeable {
    private static final CodecRegistry DEFAULT_CODEC_REGISTRY =
            fromProviders(asList(new ValueCodecProvider(),
                    new BsonValueCodecProvider(),
                    new DBRefCodecProvider(),
                    new DBObjectCodecProvider(),
                    new DocumentCodecProvider(new DocumentToDBRefTransformer()),
                    new IterableCodecProvider(new DocumentToDBRefTransformer()),
                    new MapCodecProvider(new DocumentToDBRefTransformer()),
                    new GeoJsonCodecProvider(),
                    new GridFSFileCodecProvider()));

    /**
     * Gets the default codec registry.  It includes the following providers:
     *
     * <ul>
     *     <li>{@link org.bson.codecs.ValueCodecProvider}</li>
     *     <li>{@link org.bson.codecs.BsonValueCodecProvider}</li>
     *     <li>{@link com.mongodb.DBRefCodecProvider}</li>
     *     <li>{@link com.mongodb.DBObjectCodecProvider}</li>
     *     <li>{@link org.bson.codecs.DocumentCodecProvider}</li>
     *     <li>{@link org.bson.codecs.IterableCodecProvider}</li>
     *     <li>{@link org.bson.codecs.MapCodecProvider}</li>
     *     <li>{@link com.mongodb.client.model.geojson.codecs.GeoJsonCodecProvider}</li>
     *     <li>{@link com.mongodb.client.gridfs.codecs.GridFSFileCodecProvider}</li>
     * </ul>
     *
     * @return the default codec registry
     * @see MongoClientOptions#getCodecRegistry()
     * @since 3.0
     */
    public static CodecRegistry getDefaultCodecRegistry() {
        return DEFAULT_CODEC_REGISTRY;
    }
    ...

如果不加上可能常出现一些基本对象的异常:

org.bson.codecs.configuration.CodecConfigurationException: Can't find a codec for class java.lang.Long.
    at org.bson.codecs.configuration.CodecCache.getOrThrow(CodecCache.java:46)
    at org.bson.codecs.configuration.ProvidersCodecRegistry.get(ProvidersCodecRegistry.java:63)
    at org.bson.codecs.configuration.ProvidersCodecRegistry.get(ProvidersCodecRegistry.java:37)
    at com.mongodb.client.model.BuildersHelper.encodeValue(BuildersHelper.java:35)
    at com.mongodb.client.model.Updates$SimpleUpdate.toBsonDocument(Updates.java:442)
    at com.mongodb.MongoCollectionImpl.toBsonDocument(MongoCollectionImpl.java:599)
    at com.mongodb.MongoCollectionImpl.findOneAndUpdate(MongoCollectionImpl.java:435)
    at com.mongodb.MongoCollectionImpl.findOneAndUpdate(MongoCollectionImpl.java:430)

上面的异常是说Long,也有可能是其它基本对象的包装类.

最后

[A] 解码的顺序不对可产生的异常:

org.bson.BsonSerializationException: Expected element name to be 'memberId', not 'uid'.
    at net.htage.forum.impl.test.OLRecordTest.edit(OLRecordTest.java:55)

只要将ForumMemberOnlineCodec.decode中的memberId,uid顺序倒一下即可出现,对着GUI写吧
这里写图片描述

[B] 缺少writeStartDocument和writeEndDocument方法调用可产生的异常:

org.bson.BsonInvalidOperationException: A Name value cannot be written to the root level of a BSON document.
    at org.bson.AbstractBsonWriter.throwInvalidState(AbstractBsonWriter.java:736)
    at org.bson.AbstractBsonWriter.writeName(AbstractBsonWriter.java:527)
    at org.bson.AbstractBsonWriter.writeInt64(AbstractBsonWriter.java:438)

[C] 扫描方式

CodecProvider pojoCodecProvider = PojoCodecProvider.builder().automatic(true).build();

以上代码是自动扫描,同时还可以指定包名和类.class的一个可变长参数

//包名
CodecProvider pojoCodecProvider = PojoCodecProvider.builder().register("org.example.pojos").build();
//Class Model
ClassModel<ForumMemberOnline> fmoModel = ClassModel.builder(ForumMemberOnline.class).build();
ClassModel<SequenceId> sequenceModel = ClassModel.builder(SequenceId.class).build();
CodecProvider pojoCodecProvider = PojoCodecProvider.builder().register(fmoModel, sequenceModel).build();

[D] 参考网址:

MongoDB Driver Quick Start - POJOs

Codec and CodecRegistry

3.5.0 java doc

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