• 给java mongodb 官方driver 增加bean 操作


     
    mongodb官方的java driver不支持直接插入java bean,只能使用DbObject的Key,Value形式进行insert,update,(c# mongodb官方driver类似),所以我这里加入了一个利用反射快速操作的类,来支持bean操作。另因为java不支持扩展方法,所以只能用abstract class的类来替代,c#的话可以直接扩展官方driver,会更方便。
     
    关于速度,反射(reflection)一般情况下要比直接(native)的方法要慢。先使用的是反射method赋值,平均要比native慢10%左右,所以第二次改用java 的field.set (如果是private,需先设置 field.setAccessible 为true)来进行操作,速度跟native不相上下,在模拟10万,100万数据操作的时候,有时候甚至比native还快。不过这样就舍去了一个功能是可能会在set方法中加入操作,如果需要改为的method的话(hibernate默认做法),只需要修改为method反射即可。
     
     
     
    代码很简单,写出来小记一下。 
     
    package gsralex;
    
    import java.lang.annotation.Annotation;
    import java.lang.reflect.Field;
    import java.net.UnknownHostException;
    
    import org.bson.types.ObjectId;
    
    import com.mongodb.BasicDBObject;
    import com.mongodb.DB;
    import com.mongodb.DBObject;
    import com.mongodb.Mongo;
    
    public abstract class Dao {
        private static final ThreadLocal<Mongo> threadLocal = new ThreadLocal<Mongo>();
    
        private static final String    connectAddress    = "127.0.0.1";
        private static final int    connectPort    = 27017;
    
        public static Mongo getMongo()
        {
            Mongo mongo = threadLocal.get();
            if ( mongo == null )
            {
                try {
                    mongo = new Mongo( connectAddress, connectPort );
                } catch ( UnknownHostException e ) {
    /* TODO Auto-generated catch block */
                    e.printStackTrace();
                }
                threadLocal.set( mongo );
            }
            return(mongo);
        }
    
    
        public static void close()
        {
            Mongo mongo = threadLocal.get();
    
            if ( mongo != null )
            {
                mongo.close();
                threadLocal.set( null );
            }
        }
    
    
        public static DB getDefaultDb()
        {
            return(getDb( "gsralex" ) );
        }
    
    
        public static DB getDb( String dbName )
        {
            Mongo mongo = getMongo();
    
            if ( mongo != null )
            {
                return(mongo.getDB( dbName ) );
            }
    
            return(null);
        }
    
    
        public static int insert( Object bean )
        {
            Class clazz = bean.getClass();
    
            Field[] fields = clazz.getDeclaredFields();
    
            MongoColumn    column;
            DBObject    dbObject = new BasicDBObject();
    
            try {
                for ( Field field : fields )
                {
                    column = field.getAnnotation( MongoColumn.class );
                    if ( column == null )
                    {
                        continue;
                    }
    
                    Object filedValue = field.get( bean );
                    dbObject.put( column.name(), filedValue );
                }
            } catch ( Exception e ) {
    /* TODO Auto-generated catch block */
                e.printStackTrace();
            }
    
            MongoCollection collection = (MongoCollection) clazz
                             .getAnnotation( MongoCollection.class );
            return(getDefaultDb().getCollection( collection.name() ).insert( dbObject )
                   .getN() > 0 ? 0 : -1);
        }
    
    
        public static int update( Object obj, String collectionName )
        {
            Class clazz = obj.getClass();
    
            Field[] fields = clazz.getDeclaredFields();
    
            MongoColumn    column;
            DBObject    dbObject = new BasicDBObject();
    
            try {
                for ( Field field : fields )
                {
                    column = field.getAnnotation( MongoColumn.class );
                    if ( column == null )
                    {
                        continue;
                    }
    
                    Object filedValue = field.get( obj );
                    dbObject.put( column.name(), filedValue );
                }
            } catch ( Exception e ) {
    /* TODO Auto-generated catch block */
                e.printStackTrace();
            }
    
            ObjectId _id = getObjectId( obj, clazz );
            return(getDefaultDb().getCollection( collectionName ).update(
                       new BasicDBObject( "_id", _id ), dbObject ).getN() > 0 ? 0 : -1);
        }
    
    
        private static ObjectId getObjectId( Object obj, Class clazz )
        {
            ObjectId _id = null;
            try {
                _id = (ObjectId) clazz.getField( "_id" ).get( obj );
            } catch ( Exception e ) {
    /* TODO Auto-generated catch block */
                e.printStackTrace();
            }
    
            return(_id);
        }
    
    
        public static Object getBean( DBObject dbObject, Class clazz )
        {
            if ( dbObject == null )
            {
                return(null);
            }
    
            Object obj = null;
            try {
                obj = clazz.newInstance();
    
                Field[] fields = clazz.getDeclaredFields();
    
    
                MongoColumn column;
                for ( Field field : fields )
                {
                    column = field.getAnnotation( MongoColumn.class );
    
                    if ( column == null )
                        continue;
    
                    field.setAccessible( true );
                    Object filedValue = dbObject.get( column.name() );
                    field.set( obj, filedValue );
                }
            } catch ( Exception e ) {
                e.printStackTrace();
            }
    
            return(obj);
        }
    }
     
    需要增加两个注解:
     
    package gsralex;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Target;
    
    @Target( { ElementType.TYPE } )
    public @interface MongoCollection {
        public String name() default "";
    }
    
    package gsralex;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Target;
    
    
    @Target( { ElementType.FIELD, ElementType.METHOD } )
    public @interface MongoColumn {
        public String name() default "";
    }
     

    郑州 6月23日 晴

    博客搬家从blog.163.com/gsralex 搬家到 www.cnblogs.com/gsralex
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  • 原文地址:https://www.cnblogs.com/gsralex/p/3538034.html
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