如何在Spring-Data-MongoDB框架中将BigDecimal转换为Double

Question

Spring Data MongoDB映射默认将BigDecimal转换为String。但是，我希望它们在mongodb中转换为Double。后者对于在mongodb中的此字段上进行查询（比较查询/聚合查询）是必需的。如何注册自己的转换器（BigDecimalToDouble / DoubleToBigDecimal）以执行此操作？

Answer 1

以下是添加您自己的转换器的方法：

<bean id="mongoTemplate" class="org.springframework.data.mongodb.core.MongoTemplate">
    <constructor-arg ref="mongoDbFactory"/>
    <constructor-arg ref="mappingConverter"/>
    <property name="writeConcern">
        <util:constant static-field="com.mongodb.WriteConcern.FSYNC_SAFE"/>
    </property>
    <property name="writeResultChecking">
        <util:constant static-field="org.springframework.data.mongodb.core.WriteResultChecking.EXCEPTION"/>
    </property>
</bean>

<mongo:mapping-converter id="mappingConverter">
    <mongo:custom-converters base-package="com.vladmihalcea.**.mongo.converter"/>
</mongo:mapping-converter>

现在您的转换器将如下所示：

@Component
public class DoubleToBigDecimalConverter implements Converter<Double, BigDecimal> {

    @Override
    public BigDecimal convert(Double source) {
        return new BigDecimal(source);
    }
}

@Component
public class BigDecimalToDoubleConverter implements Converter<BigDecimal, Double> {

    @Override
    public Double convert(BigDecimal source) {
        return source.doubleValue();
    }
}

在添加转换器之前我得到：

update test.product query: { _id: 123 } update: { _id: 123, _class: "com.vladmihalcea.mongo.model.Product", name: "Tv", quantity: "10", discount: "12.34", version: 0 } nscanned:0 nupdated:1 upsert:1 keyUpdates:0 locks(micros) w:49328 50ms

添加转换器后：

update test.product query: { _id: 123 } update: { _id: 123, _class: "com.vladmihalcea.mongo.model.Product", name: "Tv", quantity: "10", discount: 12.34, version: 0 } nscanned:0 nupdated:1 upsert:1 keyUpdates:0 locks(micros) w:64689 65ms