jackson 字符串转换成List集合的问题请教

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jackson 字符串转换成List集合的问题请教5

我使用了jackson先将一个List集合对象转换成json字符串后，再将json字符串转成List集合出了问题，报错信息如下：

Exception in thread "main" org.codehaus.jackson.map.JsonMappingException: No suitable constructor found for type [simple type, class com.mailbill.HDataA]: can not instantiate from JSON object (need to add/enable type information?)
 at [Source: java.io.StringReader@147917a; line: 1, column: 3]
	at org.codehaus.jackson.map.JsonMappingException.from(JsonMappingException.java:163)
	at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObjectUsingNonDefault(BeanDeserializer.java:746)
	at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:683)
	at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:580)
	at org.codehaus.jackson.map.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:217)
	at org.codehaus.jackson.map.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:194)
	at org.codehaus.jackson.map.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:30)
	at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2732)
	at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1877)
	at com.mailbill.datacore.util.JsonUtil.jacksonToCollection(JsonUtil.java:315)
	at com.mailbill.TestJson.main(TestJson.java:27)

我的List集合中的对象里有一个属性也是一个集合，代码如下：
HData.java

package com.mailbill;

import java.util.List;

public class HDataA {

	
	private String name;
	
	private String code;
	
	private List<HDataB> dataBList ;

	public String getName() {
		return name;
	}

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

	public String getCode() {
		return code;
	}

	public void setCode(String code) {
		this.code = code;
	}

	public List<HDataB> getDataBList() {
		return dataBList;
	}

	public void setDataBList(List<HDataB> dataBList) {
		this.dataBList = dataBList;
	}

	public HDataA(String name, String code, List<HDataB> dataBList) {
		super();
		this.name = name;
		this.code = code;
		this.dataBList = dataBList;
	}
	
	
}

HDataB.java:

package com.mailbill;

public class HDataB {

	
	private String name;

	public String getName() {
		return name;
	}

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

	public HDataB(String name) {
		super();
		this.name = name;
	}
	
	
}

我的测试类：

package com.mailbill;

import java.util.ArrayList;
import java.util.List;

import org.aspectj.apache.bcel.generic.ARRAYLENGTH;

import com.mailbill.datacore.util.JsonUtil;

public class TestJson {

	/**
	 * @param args
	 * @throws Exception 
	 */
	public static void main(String[] args) throws Exception {
		// TODO Auto-generated method stub
		
		List<HDataA> dataAlist = new ArrayList<HDataA>();
		List<HDataB> dataBList = new ArrayList<HDataB>();
		dataBList.add(new HDataB("hehe"));
		dataBList.add(new HDataB("xixi"));
		dataAlist.add(new HDataA("nidaye",
				"woqu", dataBList));
		String str = JsonUtil.objectToJackson(dataAlist);
		System.out.println(str);
		dataAlist = JsonUtil.jacksonToCollection(str, List.class, HDataA.class);
		if(dataAlist ==null){
			System.out.println(" dataAlist is null");
		}else{
			System.out.println(" ok ");
		}
	}

}

JsonUtion.java:


private static ObjectMapper jacksonMapper = new ObjectMapper();

public static String objectToJackson(Object obj) throws Exception {
		return jacksonMapper.writeValueAsString(obj);
	}
public static <T> T jacksonToCollection(String src,Class<?> collectionClass, Class<?>... valueType)
			throws Exception {
		JavaType javaType= jacksonMapper.getTypeFactory().constructParametricType(collectionClass, valueType); 
		return (T)jacksonMapper.readValue(src, javaType);
	}

不知道jackson如何对这类集合进行转换？

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