BeanUtils 将 java.util.Map 转换为嵌套 bean

Question

我有一个 Java bean，它有一个字段，而该字段又是另一个 bean

public class BeanOne {
   private String fieldOne;
   private BeanTwo fieldTwo;

   public String getFieldOne() {return this.fieldOne;}  
   public void setFieldOne(String fieldOne){this.fieldOne = fieldOne}

   public BeanTwo getFieldTwo() {return this.fieldTwo;}  
   public void setFieldTwo(BeanTwo fieldTwo){this.fieldTwo = fieldTwo}
}

public class BeanTwo {
   private String fieldOne;

   public String getFieldOne() {return this.fieldOne;}  
   public void setFieldOne(String fieldOne){this.fieldOne = fieldOne}
}

我正在尝试将映射传递给 BeanUtils 来尝试将以下映射转换为 BeanOne

Map beanOneMap = new HashMap<String, Object>();
beanOneMap.put("fieldOne", "fieldOneValue");
Map beanTwoMap = new HashMap<String, Object>();
beanTwoMap.put("fieldOne", "fieldOneValue");
beanOneMap.put("fieldTwo", beanTwoMap);

BeanOne beanOne = new BeanOne();
BeanUtils.populate(beanOne, beanOneMap);

但它会抛出一个错误 -

Cannot invoke BeanOne.setFieldTwo on bean class 'class Bean' - argument type mismatch - had objects of type "java.util.HashMap" but expected signature "BeanTwo"

如何使用 BeanUtils 正确填充内部 bean？

Answer 1

您应该使用 Spring 的 BeanWrapper 类。它支持嵌套属性，并可选择为您创建内部 bean：

BeanOne one = new BeanOne();
BeanWrapper wrapper = PropertyAccessorFactory.forBeanPropertyAccess(one);
wrapper.setAutoGrowNestedPaths(true);

Map<String, Object> map = new HashMap<>();
map.put("fieldOne", "fieldOneValue");
map.put("fieldTwo.fieldOne", "fieldOneValue");

wrapper.setPropertyValues(map);

assertEquals("fieldOneValue", one.getFieldOne());
BeanTwo two = one.getFieldTwo();
assertNotNull(two);
assertEquals("fieldOneValue", two.getFieldOne();

自动创建内部bean的杀手级功能是通过

wrapper.setAutoGrowNestedPaths(true)

实现的。默认值为 false，这意味着如果属性路径中的元素为 null，您将得到

NullValueInNestedPathException

。

Answer 2

我们开始，你可以这样做......

BeanOne.java

import java.util.Map;

public class BeanOne {
    private String fieldOne;
    private Map<String,BeanTwo> fieldTwo;
    public Map<String, BeanTwo> getFieldTwo() {
        return fieldTwo;
    }

    public void setFieldTwo(Map<String, BeanTwo> fieldTwo) {
        this.fieldTwo = fieldTwo;
    }

    public String getFieldOne() {
        return this.fieldOne;
    }

    public void setFieldOne(String fieldOne) {
        this.fieldOne = fieldOne;
    }
}

BeanTwo.java

public class BeanTwo {
    private String fieldOne;

    public String getFieldOne() {
        return this.fieldOne;
    }

    public void setFieldOne(String fieldOne) {
        this.fieldOne = fieldOne;
    }
}

测试器.java

import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;

import org.apache.commons.beanutils.BeanUtils;

public class Tester {
    public static void main(String[] args) throws IllegalAccessException,
            InvocationTargetException {
        Map beanTwoMap = new HashMap();
        beanTwoMap.put("fieldOne", "fieldOne2222Value");
        Map beanOneMap = new HashMap();
        beanOneMap.put("fieldOne", "fieldOneValue");
        beanOneMap.put("fieldTwo", beanTwoMap);
        BeanOne beanOne = new BeanOne();
        BeanUtils.populate(beanOne, beanOneMap);
        System.out.println(beanOne.getFieldOne());
        System.out.println(beanOne.getFieldTwo().get("fieldOne"));
    }

}

输出将是：-

fieldOneValue
fieldOne2222Value

Answer 3

public static List<SaintsDto> readYamlAndConvertToSaintsDto() {

        List<SaintsDto> saintsDtoList = new ArrayList<>();
        Yaml yaml = new Yaml();

        try (InputStream inputStream = RoughMain.class.getClassLoader().getResourceAsStream("static/saints.yml")) {
            Iterable<Object> itr = yaml.loadAll(inputStream);
            for(Object obj: itr){
                if(obj instanceof Map){
                    Map<String, Object> map = (Map<String, Object>) obj;
                    SaintsDto saintsDto = new SaintsDto();
                    PropertyAccessorFactory.forBeanPropertyAccess(saintsDto).setPropertyValues(map);
                    BeanUtils.copyProperties(map, saintsDto);
                    saintsDtoList.add(saintsDto);

                }
            }
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
        saintsDtoList.forEach(System.out::println);
        return saintsDtoList;
    }

这对我有帮助。