复杂物体的推土机映射

Question

我有 2 个 POJO，如下所示：

package com.main.java.src;

    public class SourceObj {

    protected String name;
    ...
    ...
    10 String objects

    protected Addresses addresses; 

    ...
    ...
    getter and setter for all fields

    }
---------    
package com.java.main.src;

    public class Addresses {
     protected List<Address> address;
    ...
    getters and setters

}

    package com.main.java.src;

    public class Address {
       protected String city;

       protected List<Contact> contact;

    ...

    getters & setters
    }

-----
package com.main.java.dest;
    public class DestObj {

    protected String name;
    ...
    ...
    10 String objects

    protected Addresses addresses; 

    ...
    ...
    getter and setter for all fields

    }

----------------
package com.main.java.dest;

    public class Addresses {
     protected List<Address> address;
    ...
    getters and setters
    }

package com.main.java.dest;
    public class Address {
       protected String city;

       protected List<Contact> contact;

    ...

    getters & setters
    }

Now i have the dozer-configuration.xml as follows:

    <?xml version="1.0" encoding="UTF-8"?>
    <mappings xmlns="http://dozer.sourceforge.net" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://dozer.sourceforge.net http://dozer.sourceforge.net/schema/beanmapping.xsd">
        <configuration>
            <stop-on-errors>true</stop-on-errors>
            <trim-strings>true</trim-strings>
            <relationship-type>non-cumulative</relationship-type>       
        </configuration>

        <mapping>
            <class-a>com.main.java.src.SourceObj</class-a>
            <class-b>com.main.java.dest.DestObj</class-b>
            <field>
                <a>addresses.address</a>
                <b>addresses.address</b>
                <a-hint>com.main.java.src.Address</a-hint>
                <b-hint>com.main.java.dest.Address</b-hint>
            <field> 
        </mapping>
    </mappings>

现在上面的映射将 name 等字段从 SourceObj 复制到 DestObj，但无法将 src 包的地址列表映射到 dest 包的地址列表。再次在 Address 对象中，有一个 Contact 对象列表。

我找到的一个解决方案是编写一个自定义转换器，它将原始字段值一个接一个地复制，然后将所有对象从一个列表复制到另一个目标列表。

但我正在 dozer-configuration.xml 中寻找解决方案。

在上述 xml 映射之后，我得到以下异常：

MapId: null
  Type: null
  Source parent class: com.main.java.src.SourceObj
  Source field name: addresses.address
  Source field type: class java.util.ArrayList
  Source field value: [com.main.java.src.Address@1b65d51d]
  Dest parent class: com.main.java.dest.DestObj
  Dest field name: addresses.address
  Dest field type: java.util.List

java.lang.NullPointerException: null
    at org.dozer.util.ReflectionUtils.invoke(ReflectionUtils.java:329) ~[dozer-5.5.1.jar:?]
    at org.dozer.propertydescriptor.GetterSetterPropertyDescriptor.writeDeepDestinationValue(GetterSetterPropertyDescriptor.java:268) ~[dozer-5.5.1.jar:?]
    at org.dozer.propertydescriptor.GetterSetterPropertyDescriptor.setPropertyValue(GetterSetterPropertyDescriptor.java:96) ~[dozer-5.5.1.jar:?]
    at org.dozer.fieldmap.FieldMap.writeDestValue(FieldMap.java:96) ~[dozer-5.5.1.jar:?]
    at org.dozer.MappingProcessor.writeDestinationValue(MappingProcessor.java:939) ~[dozer-5.5.1.jar:?]
    at org.dozer.MappingProcessor.mapFromFieldMap(MappingProcessor.java:368) ~[dozer-5.5.1.jar:?]
    at org.dozer.MappingProcessor.mapField(MappingProcessor.java:307) [dozer-5.5.1.jar:?]
    at org.dozer.MappingProcessor.map(MappingProcessor.java:267) [dozer-5.5.1.jar:?]
    at org.dozer.MappingProcessor.mapToDestObject(MappingProcessor.java:216) [dozer-5.5.1.jar:?]
    at org.dozer.MappingProcessor.createByCreationDirectiveAndMap(MappingProcessor.java:196) [dozer-5.5.1.jar:?]
    at org.dozer.MappingProcessor.mapGeneral(MappingProcessor.java:170) [dozer-5.5.1.jar:?]
    at org.dozer.MappingProcessor.map(MappingProcessor.java:104) [dozer-5.5.1.jar:?]
    at org.dozer.MappingProcessor.map(MappingProcessor.java:99) [dozer-5.5.1.jar:?]
    at org.dozer.DozerBeanMapper.map(DozerBeanMapper.java:120) [dozer-5.5.1.jar:?]

请告知本案的解决方案。

Answer 1

Dozer 将自动映射具有相同名称和类型的任何内容。当您要映射的字段有不同的名称时，您必须在映射中明确告诉 Dozer 哪些字段要相互映射。 在上面的问题中，AddressSrc 和 AddressDest 是具有不同名称的字段。因此，您必须明确告诉 Dozer 将这两个字段相互映射。

<mapping>
    <class-a>SourceObj</class-a>
    <class-b>DestObj</class-b>    
    <field>
        <a>addressesSrc</a>
        <b set-method="customSetMethodName">addressesDest</b>
    </field>  
</mapping>

您可能需要额外的映射说明才能获得最终想要的结果。但是，这是让 Dozer 映射这两个字段所需的缺失映射部分，因为它们具有不同的名称。

Answer 2

经过反复试验，我找到了答案。请参考以下解决方案。

<mapping>
  <class-a>com.java.main.src.SourceObj</class-a>
  <class-b>com.java.main.dest.DestObj</class-b>
  <field>><!-- java.util.List to java.util.List -->
     <a is-accessible="true">addresses.address</a>
     <b is-accessible="true">addresses.address</b>
     <a-hint>com.java.main.src.Address</a-hint>
     <b-hint>com.java.main.dest.Address</b-hint>
  </field>
</mapping>

<mapping>
  <class-a>com.java.main.src.Address</class-a>
  <class-b>com.java.main.dest.Address</class-b>
  <field>
     <a get-method="isIsPrimaryAddress">isIsPrimaryAddress</a>
     <b get-method="isIsPrimaryAddress">isIsPrimaryAddress</b>     
  </field>
</mapping>

如果对于 Address 对象，getter 方法未定义为 getFieldName，在这种情况下，您需要映射，因为我们已经映射了 isIsPrimaryAddress，如上所示。所有其他字段名称在两个地址对象中具有相同的名称，因此将自动复制值。