一种高兼容性的JavaBean序列化方案

　　在对JavaBean做序列化时，我们可能在某些场景希望前后兼容性好一些。比如所有的javaBean都序列化后保存在数据库，用的时候需要反序列化创建。随着业务的发展，数据模型可能会进行变更，那么原来的数据进行反序列化时可能会遇到版本不一致的问题。作者在对drools的Fact建模时就遇到了类似问题。那么有没有一种兼容性比较好的序列化方案同时又不失javaBean的基础特性（getter和setter函数）呢？答案是肯定的。

　　其实，简单来说，HashMap的序列化时兼容性应该是最好的，因为它就是简单的键值对，不需要版本的概念。但毕竟不是JavaBean对象，那么能不能融合着两者呢？哈哈，当然可以，废话不多说，先上代码。

public abstract class AbstractBean implements Serializable {
    protected HashMapWrapper internalHashMapData = null;

    public HashMapWrapper getInternalHashMapData() {
        return internalHashMapData;
    }

    public void setInternalHashMapData(HashMapWrapper internalHashMapData) {
        this.internalHashMapData = internalHashMapData;
    }
}

　　AbstractBean这个抽象类，保护一个HashMapWrapper的字段，用来存储所有字段的数据。

public class FirstJavaBean extends AbstractBean {
    public String getName(){
        return this.internalHashMapData.getString("name");
    }
    public void setName(String name){
        this.internalHashMapData.setString("name",name);
    }
}

　　继承AbstractBean时，包含了一个name字段，要特别注意getter和setter的实现方式。都是通过internalHashMapData存取数据的。这样做可以把数据的存储和数据的接口解耦了。如果FirstJavaBean接口变更了，对数据存取没有任何影响，序列化时就可以消除版本不一致带来的问题了！这个方法还是非常巧妙的有没有。

　　下面是对hashMap的简单封装，由于该封装后期不再变化，对序列化也不会有任何影响。

public class HashMapWrapper implements Serializable {
    private HashMap<String,Object> internalHashMap;
    public HashMapWrapper(){
        internalHashMap = new HashMap<String,Object>(0);
    }
    public void setInternalHashMap(HashMap<String,Object> hashMap){
        this.internalHashMap = hashMap;
    }
    public HashMap<String,Object> getInternalHashMap(){
        return this.internalHashMap;
    }

    public BigDecimal getBigDecimal(String key){
        return getBigDecimalOr(key,null);
    }
    public BigDecimal getBigDecimalOr(String key,BigDecimal defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof BigDecimal){
            return (BigDecimal)value;
        }else
            return defaultValue;
    }

    public void setBigDecimal(String key,BigDecimal value){
        internalHashMap.put(key,value);
    }

    public BigInteger getBigInteger(String key){
        return getBigIntegerOr(key,null);
    }
    public BigInteger getBigIntegerOr(String key,BigInteger defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof BigInteger){
            return (BigInteger)value;
        }else
            return defaultValue;
    }
    public void setBigInteger(String key,BigInteger value){
        internalHashMap.put(key,value);
    }
    public Boolean getBooleanOr(String key,Boolean defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Boolean){
            return (Boolean)value;
        }else
            return defaultValue;
    }
    public Boolean getBoolean(String key){
        return getBooleanOr(key,null);
    }

    public void setBoolean(String key,Boolean value){
        internalHashMap.put(key,value);
    }
    public Byte getByte(String key){
        return getByteOr(key,null);
    }
    public Byte getByteOr(String key,Byte defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Byte){
            return (Byte)value;
        }else
            return defaultValue;
    }

    public void setByte(String key,Byte value){
        internalHashMap.put(key,value);
    }
    public Character getCharacterOr(String key,Character defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Character){
            return (Character)value;
        }else
            return defaultValue;
    }
    public Character getCharacter(String key){
        return getCharacterOr(key,null);
    }
    public void setCharacter(String key,Character value){
        internalHashMap.put(key,value);
    }
    public Date getDateOr(String key, Date defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Date){
            return (Date)value;
        }else
            return defaultValue;
    }
    public Date getDate(String key){
        return getDateOr(key,null);
    }
    public void setDate(String key,Date value){
        internalHashMap.put(key,value);
    }

    public Double getDouble(String key){
        return getDoubleOr(key,null);
    }
    public Double getDoubleOr(String key,Double defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Double){
            return (Double)value;
        }else
            return defaultValue;
    }
    public void setDouble(String key,Double value){
        internalHashMap.put(key,value);
    }
    public Float getFloatOr(String key,Float defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Float){
            return (Float)value;
        }else
            return defaultValue;
    }
    public Float getFloat(String key){
        return getFloatOr(key,null);
    }
    public void setFloat(String key,Float value){
        internalHashMap.put(key,value);
    }
    public Integer getIntegerOr(String key,Integer defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Integer){
            return (Integer)value;
        }else
            return defaultValue;
    }
    public Integer getInteger(String key){
        return getIntegerOr(key,null);
    }
    public void setInteger(String key,Integer value){
        internalHashMap.put(key,value);
    }
    public Long getLongOr(String key,Long defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Long){
            return (Long)value;
        }else
            return defaultValue;
    }
    public Long getLong(String key){
        return getLongOr(key,null);
    }
    public void setLong(String key,Long value){
        internalHashMap.put(key,value);
    }
    public Short getShortOr(String key,Short defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Short){
            return (Short)value;
        }else
            return defaultValue;
    }
    public Short getShort(String key){
        return getShortOr(key,null);
    }
    public void setShort(String key,Short value){
        internalHashMap.put(key,value);
    }
    public String getStringOr(String key,String defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof String){
            return (String)value;
        }else
            return defaultValue;
    }
    public String getString(String key){
        return getStringOr(key,null);
    }
    public void setString(String key,String value){
        internalHashMap.put(key,value);
    }
    public boolean getBooleanValueOr(String key,boolean defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Boolean){
            return (Boolean)value;
        }else
            return defaultValue;
    }
    public boolean getBooleanValue(String key){
        return getBooleanValueOr(key,false);
    }
    public void setBooleanValue(String key,boolean value){
        internalHashMap.put(key,value);
    }
    public byte getByteValueOr(String key,byte defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Byte){
            return (Byte)value;
        }else
            return defaultValue;
    }
    public byte getByteValue(String key){
        return getByteValueOr(key,(byte)0);
    }
    public void setByteValue(String key,byte value){
        internalHashMap.put(key,value);
    }
    public char getCharValueOr(String key,char defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Character){
            return (Character)value;
        }else
            return defaultValue;
    }
    public char getCharValue(String key){
        return getCharValueOr(key,(char)0);
    }
    public void setCharValue(String key,char value){
        internalHashMap.put(key,value);
    }
    public double getDoubleValueOr(String key,double defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Double){
            return (Double)value;
        }else
            return defaultValue;
    }
    public double getDoubleValue(String key){
        return getDoubleValueOr(key,0.0d);
    }
    public void setDoubleValue(String key,double value){
        internalHashMap.put(key,value);
    }
    public float getFloatValueOr(String key,float defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Float){
            return (Float)value;
        }else
            return defaultValue;
    }
    public float getFloatValue(String key){
        return getFloatValueOr(key,0.0f);
    }
    public void setFloatValue(String key,float value){
        internalHashMap.put(key,value);
    }
    public int getIntValueOr(String key,int defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Integer){
            return (Integer)value;
        }else
            return defaultValue;
    }
    public int getIntValue(String key){
        return getIntValueOr(key,0);
    }
    public void setIntValue(String key,int value){
        internalHashMap.put(key,value);
    }
    public long getLongValueOr(String key,long defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Long){
            return (Long)value;
        }else
            return defaultValue;
    }
    public long getLongValue(String key){
        return getLongValueOr(key,0L);
    }
    public void setLongValue(String key,long value){
        internalHashMap.put(key,value);
    }
    public short getShortValueOr(String key,short defaultValue){
        Object value = internalHashMap.get(key);
        if(value instanceof Short){
            return (Short)value;
        }else
            return defaultValue;
    }
    public short getShortValue(String key){
        return getShortValueOr(key,(short)0);
    }
    public void setShortValue(String key,short value){
        internalHashMap.put(key,value);
    }
    public Object getObjectOr(String key,Object defaultValue){
        Object value = internalHashMap.get(key);
        if( value == null ){
            return defaultValue;
        }else {
            return internalHashMap.get(key);
        }
    }
    public Object getObject(String key){
        return internalHashMap.get(key);
    }
    public void setObject(String key,Object value){
        internalHashMap.put(key,value);
    }
    public <T> T getAsResultOr(String key,T defaultValue){
        T value = (T) internalHashMap.get(key);
        if(value == null){
            return defaultValue;
        }else {
            return value;
        }
    }
    public <T> T getAsResult(String key){
        return (T) internalHashMap.get(key);
    }
    public <T> void setAsValue(String key,T value){
        internalHashMap.put(key,value);
    }

    public boolean getboolean(String key) {
        return getBooleanValue(key);
    }
    public void setboolean(String key,boolean value){
        setBooleanValue(key,value);
    }
    public byte getbyte(String key) {
        return getByteValue(key);
    }
    public void setbyte(String key,byte value){
        setByteValue(key,value);
    }
    public char getchar(String key) {
        return getCharValue(key);
    }
    public void setchar(String key,char value){
        setCharValue(key,value);
    }
    public double getdouble(String key) {
        return getDoubleValue(key);
    }
    public void setdouble(String key,double value){
        setDoubleValue(key,value);
    }
    public float getfloat(String key) {
        return getFloatValue(key);
    }
    public void setfloat(String key,float value){
        setFloatValue(key,value);
    }
    public int getint(String key) {
        return getIntValue(key);
    }
    public void setint(String key,int value){
        setIntValue(key,value);
    }
    public long getlong(String key) {
        return getLongValue(key);
    }
    public void setlong(String key,long value){
        setLongValue(key,value);
    }
    public short getshort(String key) {
        return getShortValue(key);
    }
    public void setshort(String key,short value){
        setShortValue(key,value);
    }
}