关于json对象转为java对象的问题

先描述下问题：

         1、在写junit单元测试用例时，返回的json串转为java对象时不成功！出现错误提示

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.xx.xx.modules.bd.entity.xx.xx。

        2、经过debug，发现对象属性全部都自动转为LinkedHashMap了,

content值为：{"statusCode":200,"msg":"成功返回","obj":[{"id":"41","isNewRecord":false,"remarks":"","createDate":"2016-08-28 09:03:52","updateDate":"2016-08-28 09:03:52","xxList":[],"xx":"","xx":"","xx":"","xx":"01","xx":"1","xx":45,"xxList":[]}]}

 

如图：

 


 

 
 

        3、JsonResp 代码：

package com.xxx.xxx.common.json;

import java.io.Serializable;

/**
 * json 返回
 * Created by weimingjia on 2016/7/10.
 */
public class JsonResp implements Serializable{

    private int statusCode = 200; //状态码
    private String msg;
    private Object obj;

    public JsonResp(){}

    public JsonResp(int statusCode,String msg){
        this.statusCode = statusCode;
        this.msg = msg;
    }

    public JsonResp(int statusCode,String msg,Object obj){
        this.statusCode = statusCode;
        this.msg = msg;
        this.obj = obj;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public Object getObj() {
        return obj;
    }

    public void setObj(Object obj) {
        this.obj = obj;
    }

    public int getStatusCode() {
        return statusCode;
    }

    public void setStatusCode(int statusCode) {
        this.statusCode = statusCode;
    }
}

 

          4、jsonMapper代码：

 

/**
 * Copyright &copy; 2012-2014 <a href="https://github.com/thinkgem/jeesite">JeeSite</a> All rights reserved.
 */
package com.xxx.xxx.common.mapper;

import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.TimeZone;

import org.apache.commons.lang3.StringEscapeUtils;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.JsonParser.Feature;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.fasterxml.jackson.databind.util.JSONPObject;
import com.fasterxml.jackson.module.jaxb.JaxbAnnotationModule;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;

/**
 * 简单封装Jackson，实现JSON String<->Java Object的Mapper.
 * 封装不同的输出风格, 使用不同的builder函数创建实例.
 * @author ThinkGem
 * @version 2013-11-15
 */
public class JsonMapper extends ObjectMapper {

	private static final long serialVersionUID = 1L;

	private static Logger logger = LoggerFactory.getLogger(JsonMapper.class);

	private static JsonMapper mapper;

	public JsonMapper() {
		this(Include.NON_NULL);
	}

	public JsonMapper(Include include) {
		// 设置输出时包含属性的风格
		if (include != null) {
			this.setSerializationInclusion(include);
		}
		// 允许单引号、允许不带引号的字段名称
		this.enableSimple();
		// 设置输入时忽略在JSON字符串中存在但Java对象实际没有的属性
		this.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
        // 空值处理为空串
		this.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>(){
			@Override
			public void serialize(Object value, JsonGenerator jgen,
					SerializerProvider provider) throws IOException,
					JsonProcessingException {
				jgen.writeString("");
			}
        });
		// 进行HTML解码。
		/*this.registerModule(new SimpleModule().addSerializer(String.class, new JsonSerializer<String>(){
			@Override
			public void serialize(String value, JsonGenerator jgen,
					SerializerProvider provider) throws IOException,
					JsonProcessingException {
				jgen.writeString(StringEscapeUtils.unescapeHtml4(value));
			}
        }));*/
		// 设置时区
		this.setTimeZone(TimeZone.getDefault());//getTimeZone("GMT+8:00")
	}

	/**
	 * 创建只输出非Null且非Empty(如List.isEmpty)的属性到Json字符串的Mapper,建议在外部接口中使用.
	 */
	public static JsonMapper getInstance() {
		if (mapper == null){
			mapper = new JsonMapper().enableSimple();
		}
		return mapper;
	}

	/**
	 * 创建只输出初始值被改变的属性到Json字符串的Mapper, 最节约的存储方式，建议在内部接口中使用。
	 */
	public static JsonMapper nonDefaultMapper() {
		if (mapper == null){
			mapper = new JsonMapper(Include.NON_DEFAULT);
		}
		return mapper;
	}
	
	/**
	 * Object可以是POJO，也可以是Collection或数组。
	 * 如果对象为Null, 返回"null".
	 * 如果集合为空集合, 返回"[]".
	 */
	public String toJson(Object object) {
		try {
			return this.writeValueAsString(object);
		} catch (IOException e) {
			logger.warn("write to json string error:" + object, e);
			return null;
		}
	}

	/**
	 * 反序列化POJO或简单Collection如List<String>.
	 * 
	 * 如果JSON字符串为Null或"null"字符串, 返回Null.
	 * 如果JSON字符串为"[]", 返回空集合.
	 * 
	 * 如需反序列化复杂Collection如List<MyBean>, 请使用fromJson(String,JavaType)
	 * @see #fromJson(String, JavaType)
	 */
	public <T> T fromJson(String jsonString, Class<T> clazz) {
		if (StringUtils.isEmpty(jsonString)) {
			return null;
		}
		try {
			return this.readValue(jsonString, clazz);
		} catch (IOException e) {
			logger.warn("parse json string error:" + jsonString, e);
			return null;
		}
	}

	/**
	 * 反序列化复杂Collection如List<Bean>, 先使用函數createCollectionType构造类型,然后调用本函数.
	 * @see #createCollectionType(Class, Class...)
	 */
	@SuppressWarnings("unchecked")
	public <T> T fromJson(String jsonString, JavaType javaType) {
		if (StringUtils.isEmpty(jsonString)) {
			return null;
		}
		try {
			return (T) this.readValue(jsonString, javaType);
		} catch (IOException e) {
			logger.warn("parse json string error:" + jsonString, e);
			return null;
		}
	}

	/**
	 * 構造泛型的Collection Type如:
	 * ArrayList<MyBean>, 则调用constructCollectionType(ArrayList.class,MyBean.class)
	 * HashMap<String,MyBean>, 则调用(HashMap.class,String.class, MyBean.class)
	 */
	public JavaType createCollectionType(Class<?> collectionClass, Class<?>... elementClasses) {
		return this.getTypeFactory().constructParametricType(collectionClass, elementClasses);
	}

	/**
	 * 當JSON裡只含有Bean的部分屬性時，更新一個已存在Bean，只覆蓋該部分的屬性.
	 */
	@SuppressWarnings("unchecked")
	public <T> T update(String jsonString, T object) {
		try {
			return (T) this.readerForUpdating(object).readValue(jsonString);
		} catch (JsonProcessingException e) {
			logger.warn("update json string:" + jsonString + " to object:" + object + " error.", e);
		} catch (IOException e) {
			logger.warn("update json string:" + jsonString + " to object:" + object + " error.", e);
		}
		return null;
	}

	/**
	 * 輸出JSONP格式數據.
	 */
	public String toJsonP(String functionName, Object object) {
		return toJson(new JSONPObject(functionName, object));
	}

	/**
	 * 設定是否使用Enum的toString函數來讀寫Enum,
	 * 為False時時使用Enum的name()函數來讀寫Enum, 默認為False.
	 * 注意本函數一定要在Mapper創建後, 所有的讀寫動作之前調用.
	 */
	public JsonMapper enableEnumUseToString() {
		this.enable(SerializationFeature.WRITE_ENUMS_USING_TO_STRING);
		this.enable(DeserializationFeature.READ_ENUMS_USING_TO_STRING);
		return this;
	}

	/**
	 * 支持使用Jaxb的Annotation，使得POJO上的annotation不用与Jackson耦合。
	 * 默认会先查找jaxb的annotation，如果找不到再找jackson的。
	 */
	public JsonMapper enableJaxbAnnotation() {
		JaxbAnnotationModule module = new JaxbAnnotationModule();
		this.registerModule(module);
		return this;
	}

	/**
	 * 允许单引号
	 * 允许不带引号的字段名称
	 */
	public JsonMapper enableSimple() {
		this.configure(Feature.ALLOW_SINGLE_QUOTES, true);
		this.configure(Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
		return this;
	}
	
	/**
	 * 取出Mapper做进一步的设置或使用其他序列化API.
	 */
	public ObjectMapper getMapper() {
		return this;
	}

	/**
	 * 对象转换为JSON字符串
	 * @param object
	 * @return
	 */
	public static String toJsonString(Object object){
		return JsonMapper.getInstance().toJson(object);
	}
	
	/**
	 * JSON字符串转换为对象
	 * @param jsonString
	 * @param clazz
	 * @return
	 */
	public static Object fromJsonString(String jsonString, Class<?> clazz){
		return JsonMapper.getInstance().fromJson(jsonString, clazz);
	}
	
	/**
	 * 测试
	 */
	public static void main(String[] args) {
		List<Map<String, Object>> list = Lists.newArrayList();
		Map<String, Object> map = Maps.newHashMap();
		map.put("id", 1);
		map.put("pId", -1);
		map.put("name", "根节点");
		list.add(map);
		map = Maps.newHashMap();
		map.put("id", 2);
		map.put("pId", 1);
		map.put("name", "你好");
		map.put("open", true);
		list.add(map);
		String json = JsonMapper.getInstance().toJson(list);
		System.out.println(json);
	}
	
}

 

           5、单元测试用例代码：

package com.xxx.xxx.xx.xxx.xx.xx;

import com.google.common.reflect.Reflection;
import com.xxx.xxx.common.json.JsonResp;
import com.xxxx.xxx.modules.bd.entity.prescription.PactsPrescription;
import com.xxxx.xxx.modules.bd.entity.prescription.PactsTemplate;
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
import org.junit.Test;
import org.springframework.test.util.ReflectionTestUtils;
import org.springframework.test.web.servlet.MvcResult;

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

import static org.hamcrest.CoreMatchers.instanceOf;
import static org.hamcrest.core.Is.is;
import static org.hamcrest.core.IsEqual.equalTo;
import static org.hamcrest.number.OrderingComparison.greaterThan;
import static org.junit.Assert.*;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;

/**
 * Created by weimingjia on 16-8-27.
 */
public class PactsPrescriptionRestControllerTest extends PactsTemplateRestControllerTest{
    private String path = "/xxx/xx/xx/rest";

    @Test
    public void testGetPactsPrescriptionByTemplateId() throws Exception {
        Object id = getAddResponseContent();
        assertNotNull("xxx id is null",id);
        assertNotSame("xxx id is empty","",id);
        logger.info("xxx id is "+id);

        String pactsTemplateJsonAdd = String.format(pactsTemplateJson, id);
        PactsTemplate pactsTemplate = jsonMapper.fromJson(pactsTemplateJsonAdd,PactsTemplate.class);

        System.out.println(pactsTemplate);
        List<PactsPrescription> prescriptionListCorrect = pactsTemplate.getPrescriptionList();
        assertNotNull("根据json文件读取xx模板 is null",prescriptionListCorrect);
        assertThat("根据json文件读取xx模板,xx集合 is empty",prescriptionListCorrect.size(),greaterThan(0));
        PactsPrescription pactsPrescriptionCorrect = prescriptionListCorrect.get(0);

        MvcResult mvcResult= this.mockMvc.perform(get(path+"/byPactsTemplate/"+id.toString()))
                .andDo(print())
                .andExpect(jsonPath("$.statusCode").value(200))
                .andExpect(jsonPath("$.obj").value(is(instanceOf(List.class)))).andReturn();
        String content = mvcResult.getResponse().getContentAsString();

        System.out.println(content);

//        JSONObject jsonobject = JSONObject.fromObject(content);
//        JSONArray array = jsonobject.getJSONArray("obj");
//        List<PactsPrescription> prescriptionList = new ArrayList<PactsPrescription>();
//        for (int i = 0; i < array.size(); i++) {
//            JSONObject object = (JSONObject)array.get(i);
//            PactsPrescription passport = (PactsPrescription)JSONObject.toBean(object,
//                    PactsPrescription.class);
//            if(passport != null){
//                prescriptionList.add(passport);
//            }
//        }

        JsonResp jsonResp = jsonMapper.fromJson(content,JsonResp.class);
        System.out.println(jsonResp.getObj());
        List<PactsPrescription> prescriptionList = (List<PactsPrescription>)jsonResp.getObj();
        assertNotNull("根据xx模板id获取xx集合 is null",prescriptionList);
        assertThat("根据xx模板id获取xx集合 is empty",prescriptionList.size(),greaterThan(0));


        PactsPrescription pactsPrescription = prescriptionList.get(0);

        assertThat("处方名称不一致",pactsPrescription.getPrescriptionName(),equalTo(pactsPrescriptionCorrect.getPrescriptionName()));
        assertThat("处方类型不一致",pactsPrescription.getPrescriptionType(),equalTo(pactsPrescriptionCorrect.getPrescriptionType()));





    }
}

 

        解决方式一：

        1、引入jar包：

<!-- https://mvnrepository.com/artifact/com.hynnet/json-lib -->
<dependency>
   <groupId>com.hynnet</groupId>
   <artifactId>json-lib</artifactId>
   <version>2.4</version>
</dependency>

      2、将以下代码注释打开：

//        JSONObject jsonobject = JSONObject.fromObject(content);
//        JSONArray array = jsonobject.getJSONArray("obj");
//        List<PactsPrescription> prescriptionList = new ArrayList<PactsPrescription>();
//        for (int i = 0; i < array.size(); i++) {
//            JSONObject object = (JSONObject)array.get(i);
//            PactsPrescription passport = (PactsPrescription)JSONObject.toBean(object,
//                    PactsPrescription.class);
//            if(passport != null){
//                prescriptionList.add(passport);
//            }
//        }

             同时，注释以下代码：

        JsonResp jsonResp = jsonMapper.fromJson(content,JsonResp.class);
        System.out.println(jsonResp.getObj());
        List<xxx> pxxList = (List<xxx>)jsonResp.getObj();

 

至此，完成！debug如图：

 

 

 解决方式二：

     

        ObjectMapper objectMapper = new ObjectMapper();
        JsonNode rootNode = objectMapper.readTree(content);
        JsonNode objNode=rootNode.get("obj");
        String json = objectMapper.writeValueAsString(objNode);
        JavaType javaType = objectMapper.getTypeFactory().constructParametricType(
                List.class, xxx.class); 
        List<xxx> prescriptionList=objectMapper.readValue(json,javaType); 

 

 

      这种方式好处：不用重新引入新的json包，还是使用

import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;