JAXB将XML元素解组为HashMap [英] JAXB unmarshal XML elements to HashMap

问题描述

我发现了很多描述如何将一系列XML元素解组到HashMap的文章，只要它们在父元素内。然而，我没有得到这与直接根源下的孩子们一起工作！

选项1 - 作品：

 <？xml version =1.0encoding =UTF-8？> 
<支票> 
<支票> 
< check key =check1/> 
< check key =check2/> 
 ... 
< / checks> 
< / checks> 
  

选项2 - 没有 工作：

 <？xml version =1.0encoding =UTF-8？> 
<支票> 
< check key =check1/> 
< check key =check2/> 
 ... 
< / checks> 
  

支票：

  package com.foo.conf; 
 
 import java.util.Map; 
 
 import javax.xml.bind.annotation.XmlElement; 
 import javax.xml.bind.annotation.XmlRootElement; 
 import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter; 
 
 @XmlRootElement（name =checks）
 public class Checks {
 @XmlJavaTypeAdapter（ChecksAdapter.class）
 @XmlElement（name =checks）
 public Map< String，Check> checkMap; 
 
  

检查：

  package com.foo.conf; 
 
 import javax.xml.bind.annotation.XmlAttribute; 
 import javax.xml.bind.annotation.XmlValue; 
 
 public class Check {
 @XmlAttribute public String key; 
 @XmlValue public String description; 
 
 public Check（）{} 
 
 public Check（String key）{
 this.key = key; 
} 
 
 public String getCheckKey（）{
 return this.key; 
 
 
 
 
 $ b CheckMapType：
 
 
  package com.foo.conf; 
 
 import java.util.List; 
 
 import javax.xml.bind.annotation.XmlElement; 
 
 class CheckMapType {
 @XmlElement（name =check）
 public List< Check>检查表; // = new ArrayList< Check>（）; 
 
  
 ChecksAdapter：
  package com.foo.conf; 
 
 import java.util.HashMap; 
 import java.util.Map; 
 
 import javax.xml.bind.annotation.adapters.XmlAdapter; 
 
 Final class ChecksAdapter extends XmlAdapter< CheckMapType，Map< String，Check>> {
 
 @Override 
 public CheckMapType marshal（Map< String，Check> arg0）throws Exception {
 return null; 
} 
 
 @Override 
 public Map< String，Check> unmarshal（CheckMapType arg0）抛出异常{
 System.out.println（u：+ arg0.checkList.size（））; 
地图< String，Check> map = new HashMap< String，Check>（）; $（check check：arg0.checkList）{
 System.out.println（check）; 
 
 
 map.put（check.key，check）; 
} 
返回地图; 
 
 
 $ / code> 
这是（一些虚拟测试线）我如何产生类/调用解组：
 
 $ b 
  JAXBContext jc = JAXBContext.newInstance（Checks.class）; 
 Unmarshaller u = jc.createUnmarshaller（）; 
支票c =（支票）u.unmarshal（新文件（checks.xml））; 
 System.out.println（c.checkMap.size（））; 
  
有关如何获得选项＃2的任何想法？它使用List而不是Map来工作，但我需要HashMap，因为我必须通过给定的键来访问对象... 
 
 
 
任何提示都非常感谢！ / p> 
 
解决方案
 注意：我是  EclipseLink JAXB（MOXy） 负责人和  JAXB（JSR-222） 专家组。  JAXB将以嵌套关系来处理每个对象关系。  Map 被视为 Object 而不是集合 so这就是为什么你会看到你所看到的行为。
 
 
 
 MOXy有一个基于XPath的映射扩展，名为 @XmlPath 可以用于这个用例。
  package com.foo.conf; 
 
 import java.util.Map; 
 
 import javax.xml.bind.annotation.XmlElement; 
 import javax.xml.bind.annotation.XmlRootElement; 
 import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter; 
导入org.eclipse.persistence.oxm.annotations.XmlPath; 
 $ b $ @ @mlRootElement（name =checks）
 public class Checks {
 @XmlJavaTypeAdapter（ChecksAdapter.class）
 @XmlPath（。）
 public Map< String，Check> checkMap; 
} 
  
 更多信息 
 
 
 
 
 
  http ：//blog.bdoughan.com/2010/07/xpath-based-mapping.html  
 
 
  http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html  
 
 
 
I found a lot of articles that describe how to unmarshal a sequence of XML elements to a HashMap as long as they are within a "parent" element. However, I do not get this to work with the children directly under the root element!

Option 1 - Works:
<?xml version="1.0" encoding="UTF-8"?>
<checks>
  <checks>
    <check key="check1"/>
    <check key="check2"/>
    ...       
  </checks>
</checks>
Option 2 - Does not work:
<?xml version="1.0" encoding="UTF-8"?>
<checks>
  <check key="check1"/>
  <check key="check2"/>
  ...
</checks>
Checks:
package com.foo.conf;

import java.util.Map;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement; 
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

@XmlRootElement(name="checks")
public class Checks {       
    @XmlJavaTypeAdapter(ChecksAdapter.class)
    @XmlElement(name="checks")
    public Map<String, Check> checkMap;     
}
Check:
package com.foo.conf;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlValue;

public class Check {
    @XmlAttribute public String key;
    @XmlValue public String description;

    public Check() { }

    public Check(String key) {
        this.key = key;
    }

    public String getCheckKey() {
        return this.key;
    }
}
CheckMapType:
package com.foo.conf;

import java.util.List;

import javax.xml.bind.annotation.XmlElement;

class CheckMapType { 
    @XmlElement(name="check")
    public List<Check> checkList; // = new ArrayList<Check>();
}
ChecksAdapter:
package com.foo.conf;

import java.util.HashMap;
import java.util.Map;

import javax.xml.bind.annotation.adapters.XmlAdapter;

final class ChecksAdapter extends XmlAdapter<CheckMapType, Map<String, Check>> {

    @Override
    public CheckMapType marshal(Map<String, Check> arg0) throws Exception {
        return null;
    }

    @Override
    public Map<String, Check> unmarshal(CheckMapType arg0) throws Exception {
        System.out.println("u: " + arg0.checkList.size());
        Map<String, Check> map = new HashMap<String, Check>();

        for (Check check : arg0.checkList) {
            System.out.println(check);
            map.put(check.key, check);
        }
        return map;
    }       
}
This is (some dummy test lineS) how I generate the classes/invoke the unmarshalling:
JAXBContext jc = JAXBContext.newInstance(Checks.class);
Unmarshaller u = jc.createUnmarshaller();
Checks c = (Checks) u.unmarshal(new File("checks.xml"));
System.out.println(c.checkMap.size());
Any idea on how to get option #2 to work? It works when using a List instead of the Map but I need the HashMap as I have to access the objects by the given keys...

Any hints much appreciated!
解决方案
Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB (JSR-222) expert group.

JAXB will treat each object relationship with a nesting relationship.  Map is treated like an Object instead of a Collection so this is why you are getting the behaviour that you are seeing.

MOXy has an XPath based mapping extension called @XmlPath that could be used for this use case.
package com.foo.conf;

import java.util.Map;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement; 
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
import org.eclipse.persistence.oxm.annotations.XmlPath;

@XmlRootElement(name="checks")
public class Checks {       
    @XmlJavaTypeAdapter(ChecksAdapter.class)
    @XmlPath(".")
    public Map<String, Check> checkMap;     
}
For More Information


http://blog.bdoughan.com/2010/07/xpath-based-mapping.html
http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html


                        
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