java - 使用 ChronicleMap.put 时如何避免创建字节数据的新实例

Question

我正在学习如何通过使用 Byteable 键和值类来使用 ChronicleMap 3.12。当我使用基于调用堆栈的 ChronicleMap.put 操作循环运行代码时，似乎每次调用 ChronicleMap.put 时都会创建一个值对象。我假设使用 Byteable 值类将阻止对象创建。有人可以告诉我我是否可能做错了什么吗？

创建 ChronicleMap 的代码(TestDataKeyForChronicleMap 和 TestDataForChronicleMap 都是字节型的):

    map = ChronicleMap.of( TestDataKeyForChronicleMap.class, TestDataForChronicleMap.class)
            .name( "TestDataMapForChronicleMap")
            .entries(aMaxNoOfRecords).
            .create();

运行 ChronicleMap.put 时的调用堆栈

at sun.reflect.GeneratedConstructorAccessor1.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
    at net.openhft.chronicle.core.util.ObjectUtils.lambda$null$0(ObjectUtils.java:71)
    at net.openhft.chronicle.core.util.ThrowingSupplier.lambda$asSupplier$0(ThrowingSupplier.java:42)
    at net.openhft.chronicle.core.util.ObjectUtils.newInstance(ObjectUtils.java:297)
    at net.openhft.chronicle.hash.serialization.impl.InstanceCreatingMarshaller.createInstance(InstanceCreatingMarshaller.java:67)
    at net.openhft.chronicle.hash.serialization.impl.ByteableSizedReader.read(ByteableSizedReader.java:42)
    at net.openhft.chronicle.hash.serialization.impl.ByteableSizedReader.read(ByteableSizedReader.java:31)
    at net.openhft.chronicle.map.impl.CompiledMapQueryContext$EntryValueBytesData.innerGetUsing(CompiledMapQueryContext.java:585)
    at net.openhft.chronicle.map.impl.CompiledMapQueryContext$EntryValueBytesData.getUsing(CompiledMapQueryContext.java:595)
    at net.openhft.chronicle.map.impl.CompiledMapQueryContext$DefaultReturnValue.initDefaultReturnedValue(CompiledMapQueryContext.java:411)
    at net.openhft.chronicle.map.impl.CompiledMapQueryContext$DefaultReturnValue.returnValue(CompiledMapQueryContext.java:400)
    at net.openhft.chronicle.map.MapMethods.put(MapMethods.java:86)
    at net.openhft.chronicle.map.VanillaChronicleMap.put(VanillaChronicleMap.java:716)

谢谢。

更新以包含 TestDataKeyForChronicleMap:

import java.nio.BufferOverflowException;
import java.nio.BufferUnderflowException;

import net.openhft.chronicle.bytes.Byteable;
import net.openhft.chronicle.bytes.BytesStore;

public class TestDataKeyForChronicleMap implements Byteable
{
    private final static long   MAX_SIZE = 16;
    private BytesStore bytesStore;
    private long offset;

    @Override
    public BytesStore bytesStore() 
    {
        return bytesStore;
    }

    @Override
    public void bytesStore(BytesStore aBytesStore, long anOffset, long aSize)
            throws IllegalStateException, IllegalArgumentException,
            BufferOverflowException, BufferUnderflowException 
    {
        if ( aSize != MAX_SIZE )
        {
            throw new IllegalArgumentException();
        }
        bytesStore = aBytesStore;
        offset = anOffset;
    }

    @Override
    public long maxSize() 
    {
        return MAX_SIZE;
    }

    @Override
    public long offset() 
    {
        return offset;
    }

    /**
     * set key
     * @param aKey1 key 1
     * @param aKey2 key 2
     */
    public void setKey( long aKey1, long aKey2 )
    {
        bytesStore.writeLong( offset, aKey1 );
        bytesStore.writeLong( offset + 8, aKey2 );
    }

    /**
     * get key 1
     * @return key 1
     */
    public long getKey1()
    {
        return bytesStore.readLong( offset );
    }

    /**
     * get key 2
     * @return key 2
     */
    public long getKey2()
    {
        return bytesStore.readLong( offset + 8 );
    }
}

TestDataForChronicleMap 的代码:

import java.nio.BufferOverflowException;
import java.nio.BufferUnderflowException;

import net.openhft.chronicle.bytes.Byteable;
import net.openhft.chronicle.bytes.BytesStore;

public final class TestDataForChronicleMap implements TestData, Byteable
{
    private final static long   MAX_SIZE = 48;
    private BytesStore bytesStore;
    private long offset;

    public TestDataForChronicleMap()
    {
        Thread.currentThread().dumpStack();
    }

    @Override
    public BytesStore bytesStore() 
    {
        return bytesStore;
    }

    @Override
    public void bytesStore(BytesStore aBytesStore, long anOffset, long aSize)
            throws IllegalStateException, IllegalArgumentException,
            BufferOverflowException, BufferUnderflowException 
    {
        if ( aSize != MAX_SIZE )
        {
            throw new IllegalArgumentException();
        }
        bytesStore = aBytesStore;
        offset = anOffset;
    }

    @Override
    public long maxSize() 
    {
        return MAX_SIZE;
    }

    @Override
    public long offset() 
    {
        return offset;
    }

    @Override
    public void setKey(long aKey1, long aKey2) 
    {
        bytesStore.writeLong(offset+0, aKey1);
        bytesStore.writeLong(offset+8, aKey2);
        bytesStore.writeLong(offset+16, -1L);
        bytesStore.writeLong(offset+24, -1L);
        bytesStore.writeLong(offset+32, -1L);
        bytesStore.writeLong(offset+40, -1L);
    }

    @Override
    public void setData(long aKey1, long aKey2) 
    {
        bytesStore.writeLong(offset+0, aKey1);
        bytesStore.writeLong(offset+8, aKey2);
        bytesStore.writeLong(offset+16, aKey1);
        bytesStore.writeLong(offset+24, aKey2);
        bytesStore.writeLong(offset+32, aKey2);
        bytesStore.writeLong(offset+40, aKey1);
    }

    @Override
    public boolean isCorrect() 
    {
        return ( bytesStore.readLong(offset+0) ==  bytesStore.readLong(offset+16) &&  bytesStore.readLong(offset+0) ==  bytesStore.readLong(offset+40) ) 
                &&
                (  bytesStore.readLong(offset+8) ==  bytesStore.readLong(offset+24) &&  bytesStore.readLong(offset+8) ==  bytesStore.readLong(offset+32) );
    }

    @Override
    public long getKey1() 
    {
        return bytesStore.readLong(offset+0 );
    }

    @Override
    public long getKey2() 
    {
        return bytesStore.readLong(offset+8 );
    }

    @Override
    public String getPrintableText() 
    {
        StringBuilder builder = new StringBuilder();
        builder.append( bytesStore.readLong(offset+0) );
        builder.append( ' ' );
        builder.append( bytesStore.readLong(offset+8) );
        builder.append( ' ' );
        builder.append( bytesStore.readLong(offset+16) );
        builder.append( ' ' );
        builder.append( bytesStore.readLong(offset+24) );
        builder.append( ' ' );
        builder.append( bytesStore.readLong(offset+32) );
        builder.append( ' ' );
        builder.append( bytesStore.readLong(offset+40) );
        return builder.toString();
    }
}

put循环的代码:

/**
 * test add
 * @param aMap map to be used
 * @param aNoOfData no of data to be used for testing
 * @return time taken in ms
 */
public final static long TestAdd( final TestDataMap aMap, final long aNoOfData )
{
    long time = System.currentTimeMillis();
    TestData data = aMap.createTestData();
    for( long count=0; count<aNoOfData; count++ )
    {
        data.setData( count, count+aNoOfData);
        aMap.put(data);
    }
    return System.currentTimeMillis() - time;
}

TestDataMap 接口(interface)

public interface TestDataMap 
{
    /**
     * create test data
     */
    public TestData createTestData();

    /**
     * create test data for zero copy
     */
    public TestData createTestDataForZeroCopy();

    /**
     * check if map requires new data in each entry
     * @return true if new data is needed for each entry or false if data can be reused
     */
    public boolean needNewData();

    /**
     * put test data into the map
     * @param aData
     */
    public void put( TestData aData );

    /**
     * get test data from the map
     */
    public TestData get( TestData aData );

    /**
     * get test data from the map with zero copy
     */
    public boolean getZeroCopy( TestData aData );

    /**
     * remove the test data from the map
     */
    public boolean remove( TestData aData );

    /**
     * get if the map contains the test data
     */
    public boolean contains( TestData aData );

    /**
     * get size
     */
    public long getSize();

    /**
     * clear the map
     */
    public void clear();

    /**
     * dispose
     */
    public void dispose();
}

还有 TestDataMapForChronicleMap

import java.io.IOException;

import net.openhft.chronicle.bytes.BytesStore;
import net.openhft.chronicle.map.ChronicleMap;

public final class TestDataMapForChronicleMap implements TestDataMap
{
    private ChronicleMap<TestDataKeyForChronicleMap,TestDataForChronicleMap> map;
    private TestDataKeyForChronicleMap key = new TestDataKeyForChronicleMap();

    public TestDataMapForChronicleMap( long aMaxNoOfRecords ) throws IOException
    {
        map = ChronicleMap.of( TestDataKeyForChronicleMap.class, TestDataForChronicleMap.class)
                .name( "TestDataMapForChronicleMap")
                .entries(aMaxNoOfRecords)
                .putReturnsNull( true )
                .create();
        BytesStore bytesStore = BytesStore.wrap( new byte[16] );
        key.bytesStore( bytesStore, 0, bytesStore.capacity() );
    }

    /**
     * put test data into the map
     * @param aData
     */
    public void put( final TestData aData )
    {
        key.setKey( aData.getKey1(), aData.getKey2() );
        map.put( key, (TestDataForChronicleMap)aData );
    }

    /**
     * get test data from the map
     */
    public TestData get( final TestData aData )
    {
        key.setKey( aData.getKey1(), aData.getKey2() );
        return map.getUsing( key, (TestDataForChronicleMap)aData ); 
    }



/**
     * remove the test data from the map
     */
    public boolean remove( final TestData aData )
    {
        key.setKey( aData.getKey1(), aData.getKey2() );
        return map.remove( key ) != null;
    }

    /**
     * get if the map contains the test data
     */
    public boolean contains( final TestData aData )
    {
        key.setKey( aData.getKey1(), aData.getKey2() );
        return map.containsKey( key );
    }

    /**
     * dispose the map and releases all the resources
     * @param shouldRemoveFiles true will remove all the existing memory mapped files from the system
     */
    public void dispose( final boolean shouldRemoveFiles )
    {
        map.close();
    }

    /**
     * get size
     * @return size of the map
     */
    public long getSize()
    {
        return map.size();
    }

    /**
     * clear all the values from the map
     */
    public void clear()
    {
        map.clear();
    }

    @Override
    public boolean getZeroCopy(final TestData aData ) 
    {
        key.setKey( aData.getKey1(), aData.getKey2() );
        return map.getUsing( key, (TestDataForChronicleMap)aData ) != null; 
    }

    @Override
    public TestData createTestData() 
    {
        TestDataForChronicleMap data = new TestDataForChronicleMap();
        BytesStore bytesStore = BytesStore.wrap( new byte[48] );
        data.bytesStore( bytesStore, 0, bytesStore.capacity() );
        return data;
    }

    @Override
    public TestData createTestDataForZeroCopy()
    {
        //return createTestData();
        return null;
    }

    @Override
    public boolean needNewData() 
    {
        return false;
    }

    @Override
    public void dispose() 
    {
        map.close();
    }

    /**
     * get heap memory
     */
    public long getOffHeapMemory()
    {
        return map.offHeapMemoryUsed();
    }
}

测试数据代码

/**
 * TestData has the following layout
 * long key1
 * long key2
 * long value1 (value = key1)
 * long value2 (value = key2)
 * long value3 (value = key2)
 * long value4 (value = key1)
 */
public interface TestData 
{
    /**
     * set key
     * @param aKey1 key 1
     * @param aKey2 key 2
     */
    public void setKey( long aKey1, long aKey2 );

    /**
     * set data
     * @param aKey1 key 1
     * @param aKey2 key 2
     */
    public void setData( long aKey1, long aKey2 );

    /**
     * check if the data is correct
     */
    public boolean isCorrect();

    /**
     * get key 1
     * @return key 1
     */
    public long getKey1();

    /**
     * get key 2
     * @return key 2
     */
    public long getKey2();

    /**
     * to string
     */
    public String getPrintableText();
}

Answer 1

显然，您在循环中为相同的键或重复的键放置了一个值。在每个 Map.put() 上，根据 Map 契约返回先前的值(因此应该创建一个对象)。

避免这种情况的最简单方法是添加 putReturnsNull(true)到您的 ChronicleMap 配置，但这会使 ChronicleMap 违反 Map 契约(Contract)。

另一种方法是使用上下文:

static <K, V> void justPut(ChronicleMap<K, V> map, K key, V value) {
    try (ExternalMapQueryContext<K, V, ?> c = map.queryContext(key)) {
        c.updateLock().lock();
        MapEntry<K, V> entry = c.entry();
        if (entry != null) {
            c.replaceValue(entry, value);
        } else {
            c.insert(c.absentEntry(), value);
        }
    }
}