关于json对象转为java对象的有关问题
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 © 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;