给java mongodb 官方driver 增加bean 操作

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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