morhia解决BigDecimal映射问题

错误信息：morphia No usable constructor for java.math.BigDecimal

解决办法：增加自定义类型转换器，代码如下

package cn.huilink.taozhiyin.mongodb.util;

import org.mongodb.morphia.converters.TypeConverter;
import org.mongodb.morphia.mapping.MappedField;
import org.springframework.stereotype.Component;

import java.math.BigDecimal;

/**
 * Created by jifeng on 2016/8/21.
 */
@Component("decimalConverter")
public class BigDecimalConverter extends TypeConverter {

    public BigDecimalConverter() {
        super(BigDecimal.class);
    }

    @Override
    public Object encode(Object value, MappedField optionalExtraInfo) {
        BigDecimal val = (BigDecimal) value;
        if (val == null)
            return null;
        return val.toPlainString();
    }

    @Override
    public Object decode(Class targetClass, Object fromDBObject,
                         MappedField optionalExtraInfo) {
        if (fromDBObject == null)
            return null;
        BigDecimal dec = new BigDecimal(fromDBObject.toString());
        return dec;
    }

}

　　

注册类型转换器：

    /**
     * 自定义类型转换器，通过spring配置注入
     */
    private List<TypeConverter> typeConverters;

       Morphia morphia = new Morphia();
        //注入类型转换器
        if (typeConverters!=null)
            for (TypeConverter converters:typeConverters){
                morphia.getMapper().getConverters().addConverter(converters);
            }

　　spring xml注入list

        <!--自定义类型转换器-->
        <property name="typeConverters">
            <list>
                <ref bean="decimalConverter"></ref>
            </list>
        </property>

对映射的实体类BigDecimal进行用注解@Property，否则query会出错，如果分析了结果告知我一下：

java.lang.ClassCastException: java.lang.String cannot be cast to com.mongodb.DBObject

什么原因没有仔细读源码：org.mongodb.morphia.mapping.Mapper

    private void readMappedField(final Datastore datastore, final MappedField mf, final Object entity, final EntityCache cache,
                                 final DBObject dbObject) {
        if (mf.hasAnnotation(Property.class) || mf.hasAnnotation(Serialized.class)
            || mf.isTypeMongoCompatible() || getConverters().hasSimpleValueConverter(mf)) {
            opts.getValueMapper().fromDBObject(datastore, dbObject, mf, entity, cache, this);
        } else if (mf.hasAnnotation(Embedded.class)) {
            opts.getEmbeddedMapper().fromDBObject(datastore, dbObject, mf, entity, cache, this);
        } else if (mf.hasAnnotation(Reference.class)) {
            opts.getReferenceMapper().fromDBObject(datastore, dbObject, mf, entity, cache, this);
        } else {
            opts.getDefaultMapper().fromDBObject(datastore, dbObject, mf, entity, cache, this);
        }
    }

　　

　　参考资料：

http://stackoverflow.com/questions/24498011/reading-bigdecimal-with-morphia

Mongo的ORM框架的学习Morphia(十一) morphia自定义注脚、转换器的使用 http://www.myexception.cn/open-source/1014326.html