Question

我们有一个自定义数据结构，需要转换为java bean。该数据结构通常包含所有字符串，但bean将具有类型属性。

在数据结构和bean中，属性的名称相同。

bean的实际目标类型是在运行时确定的，为了增加它们，我们还需要从自定义格式的日期字符串转换为Joda DateTime对象。

没有为每种可能的类型编写方法，对此有什么好的解决方案？

由于我的代码在Spring容器中运行，我目前正在使用Springs BeanWrapper，因此我不必关心标准转换（String - ＆gt; BigDecimal等）并将其配置为：

ConversionService + custom Converter
custom PropertyEditor

然而，BeanWrapperImpl有一个说明它基本上是一个内部类，所以我对它应该如何使用或是否有其他选择感到困惑。

以下是代码：

import org.joda.time.DateTime;
import org.junit.Test;
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.core.convert.converter.Converter;
import org.springframework.core.convert.support.DefaultConversionService;

import java.beans.PropertyEditorSupport;
import java.math.BigDecimal;
import java.util.*;
import java.util.stream.Collectors;

public class BeanWrapperTest
{
    private static InputDataStructure createInputDataStructure()
    {
        return new InputDataStructure(Arrays.asList(
            map(mapEntry("name", "some name"),
                mapEntry("bigDecimal", "12.34")),
            map(mapEntry("dateTime", "2017-03-02T09:30:00.0Z"))
        ));
    }

    private Map<String, String> toMap(InputDataStructure inputDataStructure)
    {
        return inputDataStructure.data.stream()
            .flatMap(innerMap -> innerMap.entrySet().stream())
            .collect(Collectors.toMap(
                Map.Entry::getKey,
                Map.Entry::getValue
            ));
    }

    @Test
    public void copy_alternative_using_conversion_service()
    {
        // set up a conversion service and add the special date converter
        // and configure BeanWrapper with that conversion service
        DefaultConversionService defaultConversionService = new DefaultConversionService();
        defaultConversionService.addConverter(new CustomDateConverter());

        BeanWrapper beanWrapper = new BeanWrapperImpl(DestinationClass.class);
        beanWrapper.setConversionService(defaultConversionService);

        // copy all values into a Map
        // and loop over that map and use BeanWrapper to copy the properties
        Map<String, String> values = toMap(createInputDataStructure());
        values.forEach(beanWrapper::setPropertyValue);

        // bam!
        System.out.println(beanWrapper.getWrappedInstance());
    }

    @Test
    public void copy_alternative_using_formatters()
    {
        // configure BeanWrapper with a custom property editor
        BeanWrapper beanWrapper = new BeanWrapperImpl(DestinationClass.class);
        beanWrapper.registerCustomEditor(DateTime.class, new CustomDateEditor());

        // copy all values into a Map
        // and loop over that map and use BeanWrapper to copy the properties
        Map<String, String> values = toMap(createInputDataStructure());
        values.forEach(beanWrapper::setPropertyValue);

        // bam!
        System.out.println(beanWrapper.getWrappedInstance());
    }

    @SafeVarargs
    private static <K, V> Map<K, V> map(Map.Entry<K, V>... entries)
    {
        Map<K, V> map = new HashMap<>();
        for (Map.Entry<K, V> e : entries) {
            map.put(e.getKey(), e.getValue());
        }

        return map;
    }

    private static <K, V> Map.Entry<K, V> mapEntry(K key, V value)
    {
        return new AbstractMap.SimpleImmutableEntry<>(key, value);
    }

    private static class InputDataStructure
    {
        private final List<Map<String, String>> data;

        InputDataStructure(List<Map<String, String>> data)
        {
            this.data = data;
        }
    }

    private static class DestinationClass
    {
        private String name;
        private BigDecimal bigDecimal;
        private DateTime dateTime;

        public String getName()
        {
            return name;
        }

        public DestinationClass setName(String name)
        {
            this.name = name;
            return this;
        }

        public BigDecimal getBigDecimal()
        {
            return bigDecimal;
        }

        public DestinationClass setBigDecimal(BigDecimal bigDecimal)
        {
            this.bigDecimal = bigDecimal;
            return this;
        }

        public DateTime getDateTime()
        {
            return dateTime;
        }

        public DestinationClass setDateTime(DateTime dateTime)
        {
            this.dateTime = dateTime;
            return this;
        }

        @Override public String toString()
        {
            return "DestinationClass{" + "name='" + name + '\'' +
                ", bigDecimal=" + bigDecimal +
                ", dateTime=" + dateTime +
                '}';
        }
    }

    private static class CustomDateConverter implements Converter<String, DateTime>
    {
        @Override public DateTime convert(String source)
        {
            // try whatever date format would be expected
            return DateTime.parse(source);
        }
    }

    private class CustomDateEditor extends PropertyEditorSupport
    {
        @Override
        public void setAsText(String text)
        {
            // try whatever date format would be expected
            setValue(DateTime.parse(text));
        }
    }
}

Answer 1

有一种解决问题的棘手方法。您可以将对象转换为json字符串，然后使用 com.fasterxml.jackson.databind.ObjectMapper 将json字符串写入目标对象

使用Spring

1 个答案: