一 、各個JSON技術(shù)的簡介和優(yōu)劣
- json-lib
json-lib最開始的也是應(yīng)用最廣泛的json解析工具，json-lib 不好的地方確實是依賴于很多第三方包，
包括commons-beanutils.jar，commons-collections-3.2.jar，commons-lang-2.6.jar，commons-logging-1.1.1.jar，ezmorph-1.0.6.jar，
對于復雜類型的轉(zhuǎn)換，json-lib對于json轉(zhuǎn)換成bean還有缺陷，比如一個類里面會出現(xiàn)另一個類的list或者map集合，json-lib從json到bean的轉(zhuǎn)換就會出現(xiàn)問題。
json-lib在功能和性能上面都不能滿足現(xiàn)在互聯(lián)網(wǎng)化的需求。
- 開源的Jackson
相比json-lib框架，Jackson所依賴的jar包較少，簡單易用并且性能也要相對高些。
而且Jackson社區(qū)相對比較活躍，更新速度也比較快。
Jackson對于復雜類型的json轉(zhuǎn)換bean會出現(xiàn)問題，一些集合Map，List的轉(zhuǎn)換出現(xiàn)問題。
Jackson對于復雜類型的bean轉(zhuǎn)換Json，轉(zhuǎn)換的json格式不是標準的Json格式
- Google的Gson
Gson是目前功能最全的Json解析神器，Gson當初是為因應(yīng)Google公司內(nèi)部需求而由Google自行研發(fā)而來，
但自從在2008年五月公開發(fā)布第一版后已被許多公司或用戶應(yīng)用。
Gson的應(yīng)用主要為toJson與fromJson兩個轉(zhuǎn)換函數(shù)，無依賴，不需要例外額外的jar，能夠直接跑在JDK上。
而在使用這種對象轉(zhuǎn)換之前需先創(chuàng)建好對象的類型以及其成員才能成功的將JSON字符串成功轉(zhuǎn)換成相對應(yīng)的對象。
類里面只要有g(shù)et和set方法，Gson完全可以將復雜類型的json到bean或bean到j(luò)son的轉(zhuǎn)換，是JSON解析的神器。
Gson在功能上面無可挑剔，但是性能上面比FastJson有所差距。
- 阿里巴巴的FastJson
Fastjson是一個Java語言編寫的高性能的JSON處理器,由阿里巴巴公司開發(fā)。
無依賴，不需要例外額外的jar，能夠直接跑在JDK上。
FastJson在復雜類型的Bean轉(zhuǎn)換Json上會出現(xiàn)一些問題，可能會出現(xiàn)引用的類型，導致Json轉(zhuǎn)換出錯，需要制定引用。
FastJson采用獨創(chuàng)的算法，將parse的速度提升到極致，超過所有json庫。
綜上4種Json技術(shù)的比較：在項目選型的時候可以使用Google的Gson和阿里巴巴的FastJson兩種并行使用，
如果只是功能要求，沒有性能要求，可以使用google的Gson，
如果有性能上面的要求可以使用Gson將bean轉(zhuǎn)換json確保數(shù)據(jù)的正確，使用FastJson將Json轉(zhuǎn)換Bean
二、Google的Gson包的使用簡介。
2.1 主要類介紹
Gson類：解析json的最基礎(chǔ)的工具類
JsonParser類：解析器來解析JSON到JsonElements的解析樹
JsonElement類：一個類代表的JSON元素
JsonObject類：JSON對象類型
JsonArray類：JsonObject數(shù)組
TypeToken類：用于創(chuàng)建type，比如泛型List<?>
2.2 maven依賴
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.0</version>
</dependency>
2.3 bean轉(zhuǎn)換json
Gson gson = new Gson();
String json = gson.toJson(obj);
//obj是對象
2.4 json轉(zhuǎn)換bean
Gson gson = new Gson();
String json = "{\"id\":\"2\",\"name\":\"Json技術(shù)\"}";
Book book = gson.fromJson(json, Book.class);
2.5 json轉(zhuǎn)換復雜的bean，比如List，Set
將json轉(zhuǎn)換成復雜類型的bean,需要使用TypeToken
Gson gson = new Gson();
String json = "[{\"id\":\"1\",\"name\":\"Json技術(shù)\"},{\"id\":\"2\",\"name\":\"java技術(shù)\"}]";
//將json轉(zhuǎn)換成List
List list = gson.fromJson(json,new TypeToken<LIST>() {}.getType());
//將json轉(zhuǎn)換成Set
Set set = gson.fromJson(json,new TypeToken<SET>() {}.getType());
2.6 通過json對象直接操作json以及一些json的工具
a) 格式化Json
String json = "[{\"id\":\"1\",\"name\":\"Json技術(shù)\"},{\"id\":\"2\",\"name\":\"java技術(shù)\"}]";
Gson gson = new GsonBuilder().setPrettyPrinting().create();
JsonParser jp = new JsonParser();
JsonElement je = jp.parse(json);
json = gson.toJson(je);
b) 判斷字符串是否是json,通過捕捉的異常來判斷是否是json
String json = "[{\"id\":\"1\",\"name\":\"Json技術(shù)\"},{\"id\":\"2\",\"name\":\"java技術(shù)\"}]";
boolean jsonFlag;
try {
new JsonParser().parse(str).getAsJsonObject();
jsonFlag = true;
} catch (Exception e) {
jsonFlag = false;
}
c) 從json串中獲取屬性
String json = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
String propertyName = 'id';
String propertyValue = "";
try {
JsonParser jsonParser = new JsonParser();
JsonElement element = jsonParser.parse(json);
JsonObject jsonObj = element.getAsJsonObject();
propertyValue = jsonObj.get(propertyName).toString();
} catch (Exception e) {
propertyValue = null;
}
d) 除去json中的某個屬性
String json = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
String propertyName = 'id';
JsonParser jsonParser = new JsonParser();
JsonElement element = jsonParser.parse(json);
JsonObject jsonObj = element.getAsJsonObject();
jsonObj.remove(propertyName);
json = jsonObj.toString();
e) 向json中添加屬性
String json = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
String propertyName = 'desc';
Object propertyValue = "json各種技術(shù)的調(diào)研";
JsonParser jsonParser = new JsonParser();
JsonElement element = jsonParser.parse(json);
JsonObject jsonObj = element.getAsJsonObject();
jsonObj.addProperty(propertyName, new Gson().toJson(propertyValue));
json = jsonObj.toString();
f) 修改json中的屬性
String json = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
String propertyName = 'name';
Object propertyValue = "json各種技術(shù)的調(diào)研";
JsonParser jsonParser = new JsonParser();
JsonElement element = jsonParser.parse(json);
JsonObject jsonObj = element.getAsJsonObject();
jsonObj.remove(propertyName);
jsonObj.addProperty(propertyName, new Gson().toJson(propertyValue));
json = jsonObj.toString();
g) 判斷json中是否有屬性
String json = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
String propertyName = 'name';
boolean isContains = false ;
JsonParser jsonParser = new JsonParser();
JsonElement element = jsonParser.parse(json);
JsonObject jsonObj = element.getAsJsonObject();
isContains = jsonObj.has(propertyName);
h) json中日期格式的處理
GsonBuilder builder = new GsonBuilder();
builder.setDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
Gson gson = builder.create();
然后使用gson對象進行json的處理，如果出現(xiàn)日期Date類的對象，就會按照設(shè)置的格式進行處理
i) json中對于Html的轉(zhuǎn)義
Gson gson = new Gson();
這種對象默認對Html進行轉(zhuǎn)義，如果不想轉(zhuǎn)義使用下面的方法
GsonBuilder builder = new GsonBuilder();
builder.disableHtmlEscaping();
Gson gson = builder.create();
三、阿里巴巴的FastJson包的使用簡介。
3.1 maven依賴
<!-- FastJson將Json轉(zhuǎn)換Bean -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.46</version>
</dependency>
3.2 基礎(chǔ)轉(zhuǎn)換類
同上
3.3 bean轉(zhuǎn)換json
將對象轉(zhuǎn)換成格式化的json
JSON.toJSONString(obj,true);
將對象轉(zhuǎn)換成非格式化的json
JSON.toJSONString(obj,false);
obj設(shè)計對象
對于復雜類型的轉(zhuǎn)換,對于重復的引用在轉(zhuǎn)成json串后在json串中出現(xiàn)引用的字符,比如 [0].books[1]
Student stu = new Student();
Set books= new HashSet();
Book book = new Book();
books.add(book);
stu.setBooks(books);
List list = new ArrayList();
for(int i=0;i<5;i++)
list.add(stu);
String json = JSON.toJSONString(list,true);
3.4 json轉(zhuǎn)換bean
String json = "{\"id\":\"2\",\"name\":\"Json技術(shù)\"}";
Book book = JSON.parseObject(json, Book.class);
3.5 json轉(zhuǎn)換復雜的bean，比如List，Map
String json = "[{\"id\":\"1\",\"name\":\"Json技術(shù)\"},{\"id\":\"2\",\"name\":\"java技術(shù)\"}]";
//將json轉(zhuǎn)換成List
List list = JSON.parseObject(json,new TypeReference<ARRAYLIST>(){});
//將json轉(zhuǎn)換成Set
Set set = JSON.parseObject(json,new TypeReference<HASHSET>(){});
3.6 通過json對象直接操作json
a) 從json串中獲取屬性
String propertyName = 'id';
String propertyValue = "";
String json = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
JSONObject obj = JSON.parseObject(json);
propertyValue = obj.get(propertyName));
b) 除去json中的某個屬性
String propertyName = 'id';
String propertyValue = "";
String json = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
JSONObject obj = JSON.parseObject(json);
Set set = obj.keySet();
propertyValue = set.remove(propertyName);
json = obj.toString();
c) 向json中添加屬性
String propertyName = 'desc';
Object propertyValue = "json的玩意兒";
String json = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
JSONObject obj = JSON.parseObject(json);
obj.put(propertyName, JSON.toJSONString(propertyValue));
json = obj.toString();
d) 修改json中的屬性
String propertyName = 'name';
Object propertyValue = "json的玩意兒";
String json = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
JSONObject obj = JSON.parseObject(json);
Set set = obj.keySet();
if(set.contains(propertyName))
obj.put(propertyName, JSON.toJSONString(propertyValue));
json = obj.toString();
e) 判斷json中是否有屬性
String propertyName = 'name';
boolean isContain = false;
String json = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
JSONObject obj = JSON.parseObject(json);
Set set = obj.keySet();
isContain = set.contains(propertyName);
f) json中日期格式的處理
Object obj = new Date();
String json = JSON.toJSONStringWithDateFormat(obj, "yyyy-MM-dd HH:mm:ss.SSS");
使用JSON.toJSONStringWithDateFormat,該方法可以使用設(shè)置的日期格式對日期進行轉(zhuǎn)換
四、json-lib包的使用簡介。
4.1 maven依賴
//json-lib 為官方api，只需java jdk >jdk15即可。需要依賴一下jar包
<dependency>
<groupId>commons-beanutils</groupId>
<artifactId>commons-beanutils</artifactId>
<version>1.8.0</version>
</dependency>
<dependency>
<groupId>commons-collections</groupId>
<artifactId>commons-collections</artifactId>
<version>3.2.1</version>
</dependency>
<dependency>
<groupId>commons-lang</groupId>
<artifactId>commons-lang</artifactId>
<version>2.6</version>
</dependency>
<!-- slf4j日志依賴 -->
<dependency>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
<version>1.2</version>
</dependency>
4.2 基礎(chǔ)轉(zhuǎn)換類
同上
4.3 bean轉(zhuǎn)換json
a)將類轉(zhuǎn)換成Json,obj是普通的對象，不是List，Map的對象
String json = JSONObject.fromObject(obj).toString();
b) 將List，Map轉(zhuǎn)換成Json
String json = JSONArray.fromObject(list).toString();
String json = JSONArray.fromObject(map).toString();
4.4 json轉(zhuǎn)換bean
String json = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
JSONObject jsonObj = JSONObject.fromObject(json);
Book book = (Book)JSONObject.toBean(jsonObj,Book.class);
4.5 json轉(zhuǎn)換List,對于復雜類型的轉(zhuǎn)換會出現(xiàn)問題
String json = "[{\"id\":\"1\",\"name\":\"Json技術(shù)\"},{\"id\":\"2\",\"name\":\"Java技術(shù)\"}]";
JSONArray jsonArray = JSONArray.fromObject(json);
JSONObject jsonObject;
T bean;
int size = jsonArray.size();
List list = new ArrayList(size);
for (int i = 0; i < size; i++) {
jsonObject = jsonArray.getJSONObject(i);
bean = (T) JSONObject.toBean(jsonObject, beanClass);
list.add(bean);
}
4.6 json轉(zhuǎn)換Map
String jsonString = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
JSONObject jsonObject = JSONObject.fromObject(jsonString);
Iterator keyIter = jsonObject.keys();
String key;
Object value;
Map valueMap = new HashMap();
while (keyIter.hasNext()) {
key = (String) keyIter.next();
value = jsonObject.get(key).toString();
valueMap.put(key, value);
}
4.7 json對于日期的操作比較復雜，需要使用JsonConfig,比Gson和FastJson要麻煩多了
創(chuàng)建轉(zhuǎn)換的接口實現(xiàn)類，轉(zhuǎn)換成指定格式的日期
class DateJsonValueProcessor implements JsonValueProcessor{
public static final String DEFAULT_DATE_PATTERN = "yyyy-MM-dd HH:mm:ss.SSS";
private DateFormat dateFormat;
public DateJsonValueProcessor(String datePattern) {
try {
dateFormat = new SimpleDateFormat(datePattern);
} catch (Exception ex) {
dateFormat = new SimpleDateFormat(DEFAULT_DATE_PATTERN);
}
}
public Object processArrayValue(Object value, JsonConfig jsonConfig) {
return process(value);
}
public Object processObjectValue(String key, Object value,
JsonConfig jsonConfig) {
return process(value);
}
private Object process(Object value) {
return dateFormat.format[1];
Map<STRING,DATE> birthDays = new HashMap<STRING,DATE>();
birthDays.put("WolfKing",new Date());
JSONObject jsonObject = JSONObject.fromObject(birthDays, jsonConfig);
String json = jsonObject.toString();
System.out.println(json);
}
}
4.8 JsonObject 對于json的操作和處理
a) 從json串中獲取屬性
String jsonString = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
Object key = "name";
Object value = null;
JSONObject jsonObject = JSONObject.fromObject(jsonString);
value = jsonObject.get(key);
jsonString = jsonObject.toString();
b) 除去json中的某個屬性
String jsonString = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
Object key = "name";
Object value = null;
JSONObject jsonObject = JSONObject.fromObject(jsonString);
value = jsonObject.remove(key);
jsonString = jsonObject.toString();
c) 向json中添加和修改屬性，有則修改，無則添加
String jsonString = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
Object key = "desc";
Object value = "json的好東西";
JSONObject jsonObject = JSONObject.fromObject(jsonString);
jsonObject.put(key,value);
jsonString = jsonObject.toString();
d) 判斷json中是否有屬性
String jsonString = "{\"id\":\"1\",\"name\":\"Json技術(shù)\"}";
boolean containFlag = false;
Object key = "desc";
JSONObject jsonObject = JSONObject.fromObject(jsonString);
containFlag = jsonObject.containsKey(key);
五、注意事項
fastjson 和 jackson 在把對象序列化成json字符串的時候，是通過反射遍歷出該類中的所有g(shù)etter方法；
Gson 是通過反射遍歷該類中的所有屬性。
所以，在定義POJO中的布爾類型的變量時，不要使用isSuccess這種形式，而要直接使用success 。
六、示例
以上為網(wǎng)上摘抄，以下為實際項目中使用結(jié)果。
實體類為BaseVO.java:
package com.zr.workflow.activiti.entity;
import java.io.Serializable;
import java.util.Date;
import java.util.List;
import org.activiti.engine.history.HistoricProcessInstance;
import org.activiti.engine.history.HistoricTaskInstance;
import org.activiti.engine.repository.ProcessDefinition;
import org.activiti.engine.runtime.ProcessInstance;
import org.activiti.engine.task.Task;
import com.alibaba.fastjson.JSONObject;
import com.zr.workflow.activiti.util.DateFormatUtil;
public class BaseVO implements Serializable {
private static final long serialVersionUID = 6165121688276341503L;
protected int id;
protected String createId;// 創(chuàng)建人
protected String createName;
protected String createTime;// 流程的創(chuàng)建時間
protected String endTime;// 流程的結(jié)束時間
protected String reason;
protected String owner;// 擁有者
// 申請的標題
protected String title;
// 業(yè)務(wù)類型
protected String businessType;
protected String deploymentId;// 流程部署id
protected String processInstanceId;// 流程實例id
protected String deleteReason;// 刪除原因
protected String handledTaskId;// 已處理任務(wù)id
protected String handledTaskDefinitionKey;// 已處理節(jié)點
protected String handledTaskName;// 已處理節(jié)點名稱
protected String assignedId;// 已處理節(jié)點的受理人
protected String assignedName;// 已處理節(jié)點的受理人
protected String toHandleTaskId;// 當前節(jié)點的任務(wù)id
protected String taskDefinitionKey;// 當前節(jié)點key
protected String toHandleTaskName;// 當前節(jié)點點名
protected String assign;// 當前節(jié)點的受理人
protected String assignName;// 當前節(jié)點的受理人
protected String description;// 描述
protected String businessKey;// 對應(yīng)業(yè)務(wù)的id
protected String startTime;// 任務(wù)的開始時間
protected String operateTime;// 任務(wù)的結(jié)束時間(處理時間)
protected String claimTime;// 任務(wù)的簽收時間
protected boolean isEnd;// 流程是否結(jié)束
protected boolean isSuspended;// 是否掛起
protected String processDefinitionId;// 流程定義id
protected String processDefinitionName;// 流程名稱
protected String processDefinitionKey;// 流程key，任務(wù)跳轉(zhuǎn)用
protected String processStatus;// 流程狀態(tài)：待審批、審批通過、審批退回、歸檔、結(jié)束
protected int version;// 流程版本號
protected JSONObject contentInfo;// 流程的業(yè)務(wù)相關(guān)
private String candidate_ids;//下一節(jié)點執(zhí)行人,多個用逗號隔開
private String candidate_names;//下一節(jié)點執(zhí)行人,多個用逗號隔開
private List<CommentVO> comments;//評論列表
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getCreateId() {
return createId;
}
public void setCreateId(String createId) {
this.createId = createId;
}
public String getCreateName() {
return createName;
}
public void setCreateName(String createName) {
this.createName = createName;
}
public String getReason() {
return reason;
}
public void setReason(String reason) {
this.reason = reason;
}
public String getOwner() {
if (this.owner == null) {
this.owner = (null == task) ? "" : task.getOwner();
}
return owner;
}
public void setOwner(String owner) {
this.owner = owner;
}
public String getCreateTime() {
return createTime;
}
public void setCreateTime(String createTime) {
this.createTime = createTime;
}
public String getEndTime() {
if (this.endTime == null) {
Date endDate = (null == historicProcessInstance) ? null : historicProcessInstance.getEndTime();
endTime = endDate == null ? "" : DateFormatUtil.format(endDate);
}
return endTime;
}
public void setEndTime(String endTime) {
this.endTime = endTime;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getBusinessType() {
return businessType;
}
public void setBusinessType(String businessType) {
this.businessType = businessType;
}
public String getDeploymentId() {
if (this.deploymentId == null) {
this.deploymentId = (null == processInstance) ? "" : processInstance.getDeploymentId();
}
return deploymentId;
}
public void setDeploymentId(String deploymentId) {
this.deploymentId = deploymentId;
}
public String getProcessInstanceId() {
if (this.processInstanceId == null || "".equals(this.processInstanceId)) {
if (historicTaskInstance != null) {
this.processInstanceId = historicTaskInstance.getProcessInstanceId();
} else if (processInstance != null) {
this.processInstanceId = processInstance.getId();
} else {
this.processInstanceId = (null == historicProcessInstance) ? "" : historicProcessInstance.getId();
}
}
return processInstanceId;
}
public void setProcessInstanceId(String processInstanceId) {
this.processInstanceId = processInstanceId;
}
public String getDeleteReason() {
if (this.deleteReason == null) {
this.deleteReason = (null == historicTaskInstance) ? "" : historicTaskInstance.getDeleteReason();
}
return deleteReason;
}
public void setDeleteReason(String deleteReason) {
this.deleteReason = deleteReason;
}
public String getHandledTaskId() {
if (this.handledTaskId == null) {
this.handledTaskId = (null == historicTaskInstance) ? "" : historicTaskInstance.getId();
}
return handledTaskId;
}
public void setHandledTaskId(String handledTaskId) {
this.handledTaskId = handledTaskId;
}
public String getHandledTaskDefinitionKey() {
if (this.handledTaskDefinitionKey == null) {
this.handledTaskDefinitionKey = (null == historicTaskInstance) ? ""
: historicTaskInstance.getTaskDefinitionKey();
}
return handledTaskDefinitionKey;
}
public void setHandledTaskDefinitionKey(String handledTaskDefinitionKey) {
this.handledTaskDefinitionKey = handledTaskDefinitionKey;
}
public String getHandledTaskName() {
if (this.handledTaskName == null) {
this.handledTaskName = (null == historicTaskInstance) ? "" : historicTaskInstance.getName();
}
return handledTaskName;
}
public void setHandledTaskName(String handledTaskName) {
this.handledTaskName = handledTaskName;
}
public String getAssignedId() {
if (this.assignedId == null) {
this.assignedId = (null == historicTaskInstance) ? "" : historicTaskInstance.getAssignee();
}
return assignedId;
}
public void setAssignedId(String assignedId) {
this.assignedId = assignedId;
}
public String getAssignedName() {
return assignedName;
}
public void setAssignedName(String assignedName) {
this.assignedName = assignedName;
}
public String getToHandleTaskId() {
if (this.toHandleTaskId == null) {
this.toHandleTaskId = (null == task) ? "" : task.getId();
}
return toHandleTaskId;
}
public void setToHandleTaskId(String toHandleTaskId) {
this.toHandleTaskId = toHandleTaskId;
}
public String getTaskDefinitionKey() {
if (this.taskDefinitionKey == null) {
this.taskDefinitionKey = (null == task) ? "" : task.getTaskDefinitionKey();
}
return taskDefinitionKey;
}
public void setTaskDefinitionKey(String taskDefinitionKey) {
this.taskDefinitionKey = taskDefinitionKey;
}
public String getToHandleTaskName() {
if (this.toHandleTaskName == null) {
this.toHandleTaskName = (null == task) ? "" : task.getName();
}
return toHandleTaskName;
}
public void setToHandleTaskName(String toHandleTaskName) {
this.toHandleTaskName = toHandleTaskName;
}
public String getAssign() {
if (this.assign == null) {
this.assign = (null == task) ? "" : task.getAssignee();
}
return assign;
}
public void setAssign(String assign) {
this.assign = assign;
}
public String getAssignName() {
return assignName;
}
public void setAssignName(String assignName) {
this.assignName = assignName;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getBusinessKey() {
return businessKey;
}
public void setBusinessKey(String businessKey) {
this.businessKey = businessKey;
}
public String getStartTime() {
if (this.startTime == null) {
Date startDate = null;
if (historicTaskInstance != null) {
startDate = historicTaskInstance.getStartTime();
} else {
startDate = (null == historicProcessInstance) ? null : historicProcessInstance.getStartTime();
}
startTime = startDate == null ? "" : DateFormatUtil.format(startDate);
}
return startTime;
}
public void setStartTime(String startTime) {
this.startTime = startTime;
}
public String getOperateTime() {
if (this.operateTime == null) {
Date operateDate = (null == historicTaskInstance) ? null : historicTaskInstance.getEndTime();
operateTime = operateDate == null ? "" : DateFormatUtil.format(operateDate);
}
return operateTime;
}
public void setOperateTime(String operateTime) {
this.operateTime = endTime;
}
public String getClaimTime() {
if (this.claimTime == null) {
Date claimDate = (null == historicTaskInstance) ? null : historicTaskInstance.getClaimTime();
claimTime = claimDate == null ? "" : DateFormatUtil.format(claimDate);
}
return claimTime;
}
public void setClaimTime(String claimTime) {
this.claimTime = claimTime;
}
public boolean isEnd() {
return isEnd;
}
public void setEnd(boolean isEnd) {
this.isEnd = isEnd;
}
public boolean isSuspended() {
this.isSuspended = (null == processInstance) ? isSuspended : processInstance.isSuspended();
return isSuspended;
}
public void setSuspended(boolean isSuspended) {
this.isSuspended = isSuspended;
}
public String getProcessDefinitionId() {
if (processDefinitionId == null) {
if (processInstance != null) {
this.processDefinitionId = processInstance.getProcessDefinitionId();
} else {
this.processDefinitionId = (null == historicProcessInstance) ? ""
: historicProcessInstance.getProcessDefinitionId();
}
}
return processDefinitionId;
}
public void setProcessDefinitionId(String processDefinitionId) {
this.processDefinitionId = processDefinitionId;
}
public String getProcessDefinitionName() {
if (processDefinitionName == null) {
this.processDefinitionName = (null == processDefinition) ? "" : processDefinition.getName();
}
return processDefinitionName;
}
public void setProcessDefinitionName(String processDefinitionName) {
this.processDefinitionName = processDefinitionName;
}
public String getProcessDefinitionKey() {
if (processDefinitionKey == null) {
this.processDefinitionKey = (null == processDefinition) ? "" : processDefinition.getKey();
}
return processDefinitionKey;
}
public void setProcessDefinitionKey(String processDefinitionKey) {
this.processDefinitionKey = processDefinitionKey;
}
public String getProcessStatus() {
return processStatus;
}
public void setProcessStatus(String processStatus) {
this.processStatus = processStatus;
}
public int getVersion() {
if(version <= 0) {
version = (null == processDefinition) ? 0 : processDefinition.getVersion();
}
return version;
}
public void setVersion(int version) {
this.version = version;
}
public JSONObject getContentInfo() {
return contentInfo;
}
public void setContentInfo(JSONObject contentInfo) {
this.contentInfo = contentInfo;
}
public String getCandidate_ids() {
return null == candidate_ids ? null : candidate_ids.replaceAll("\\[", "").replaceAll("\"", "").replaceAll("\\]", "");
}
public void setCandidate_ids(String candidate_ids) {
this.candidate_ids = candidate_ids;
}
public String getCandidate_names() {
return null == candidate_names ? null : candidate_names.replaceAll("\\[", "").replaceAll("\"", "").replaceAll("\\]", "");
}
public void setCandidate_names(String candidate_names) {
this.candidate_names = candidate_names;
}
public void setComments(List<CommentVO> commentList) {
this.comments = commentList;
}
public List<CommentVO> getComments(){
return comments;
}
// 流程任務(wù)
public Task task;
// 運行中的流程實例
protected ProcessInstance processInstance;
// 歷史的流程實例
protected HistoricProcessInstance historicProcessInstance;
// 歷史任務(wù)
protected HistoricTaskInstance historicTaskInstance;
// 流程定義
protected ProcessDefinition processDefinition;
public void setTask(Task task) {
this.task = task;
}
public void setProcessInstance(ProcessInstance processInstance) {
this.processInstance = processInstance;
}
public void setHistoricProcessInstance(HistoricProcessInstance historicProcessInstance) {
this.historicProcessInstance = historicProcessInstance;
}
public void setProcessDefinition(ProcessDefinition processDefinition) {
this.processDefinition = processDefinition;
}
public void setHistoricTaskInstance(HistoricTaskInstance historicTaskInstance) {
this.historicTaskInstance = historicTaskInstance;
}
}
用Gson 將該實體類轉(zhuǎn)成json時報以下異常：
java.lang.IllegalArgumentException: class org.activiti.engine.impl.persistence.entity.ProcessDefinitionEntity declares multiple JSON fields named key
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:170)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:100)
at com.google.gson.Gson.getAdapter(Gson.java:423)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.createBoundField(ReflectiveTypeAdapterFactory.java:115)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:164)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:100)
at com.google.gson.Gson.getAdapter(Gson.java:423)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory.create(CollectionTypeAdapterFactory.java:53)
at com.google.gson.Gson.getAdapter(Gson.java:423)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.createBoundField(ReflectiveTypeAdapterFactory.java:115)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:164)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:100)
at com.google.gson.Gson.getAdapter(Gson.java:423)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:56)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:125)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:243)
at com.google.gson.internal.bind.ObjectTypeAdapter.write(ObjectTypeAdapter.java:107)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:97)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:61)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.write(MapTypeAdapterFactory.java:208)
at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.write(MapTypeAdapterFactory.java:145)
at com.google.gson.Gson.toJson(Gson.java:669)
at com.google.gson.Gson.toJson(Gson.java:648)
at com.google.gson.Gson.toJson(Gson.java:603)
at com.google.gson.Gson.toJson(Gson.java:583)
at net.northking.activiti.util.JsonUtil.toJson(JsonUtil.java:47)
原因是：子類和父類有相同的字段屬性;
解決方法：
(1)重命名重復字段。因為重復的字段在第三方包中，所以該方法在本例中不可行。
(2)將實體類中需要打印的字段加上注解@Expose，（本例將該類所有有g(shù)et方法的屬性都加上了） ：
@Expose
protected int id;
@Expose
protected String createId;// 創(chuàng)建人
@Expose
protected String createName;
新建gson：
Gson gson = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create();
String json = gson.toJson(obj);
excludeFieldsWithoutExposeAnnotation排除掉沒有Expose注解的屬性。
或者在不需要解析的字段前面加上transient:
// 流程任務(wù)
public transient Task task;
// 運行中的流程實例
protected transient ProcessInstance processInstance;
// 歷史的流程實例
protected transient HistoricProcessInstance historicProcessInstance;
// 歷史任務(wù)
protected transient HistoricTaskInstance historicTaskInstance;
// 流程定義
protected transient ProcessDefinition processDefinition;
用該方式，沒有報異常了，解析結(jié)果（加注解@Expose或加transient）如下：
{
"data": [{
"id": 0,
"createId": "admin",
"createName": "系統(tǒng)管理員",
"createTime": "2019-04-11 17:01:46",
"reason": "",
"title": "2019-04-01至2019-04-07工時填報",
"processInstanceId": "70013",
"handledTaskId": "70023",
"handledTaskDefinitionKey": "outsourcerApply",
"handledTaskName": "外包人員申請",
"assignedId": "admin",
"assignedName": "系統(tǒng)管理員",
"toHandleTaskId": "70039",
"taskDefinitionKey": "projectManagerAudit",
"toHandleTaskName": "項目經(jīng)理審批",
"assign": "215",
"assignName": "郭俊杰",
"description": "您提出2019-04-01至2019-04-07工時填報",
"businessKey": "monthlyreportForProjectProcess:admin:20190401:20190407",
"isEnd": false,
"isSuspended": false,
"processDefinitionId": "monthlyreportForProjectProcess:1:70012",
"processDefinitionName": "工時填報（項目外包/行內(nèi)人員）",
"processDefinitionKey": "monthlyreportForProjectProcess",
"processStatus": "WAITING_FOR_APPROVAL",
"version": 0,
"contentInfo": {
"contentInfoId": "39a14c350fa64a3ca26a50b4531307c6",
"ssoUser": "1",
"reportId": "39a14c350fa64a3ca26a50b4531307c6",
"createTime": "2019-04-11",
"reportRemark": "",
"reportStatus": "1",
"project": [{
"hoursTime": "5",
"percentTime": "0",
"managerId": "215",
"projectName": "其他",
"projectId": "other"
}],
"startTime": "2019-04-01",
"endTime": "2019-04-07",
"flowFlag": "create",
"userId": "admin"
},
"candidate_ids": "",
"candidate_names": "",
"comments": [{
"id": "70024",
"userId": "admin",
"userName": "系統(tǒng)管理員",
"content": "發(fā)起申請",
"taskId": "70023",
"processInstanceId": "70013",
"time": "2019-04-11 17:01:47",
"nextAssign": "215",
"nextAssignName": "郭俊杰"
}]
}],
"type": "success"
}
但從結(jié)果來看，那些直接調(diào)用第三方api獲取值的屬性沒有解析，因為第三方的類無法加上@Expose注解，導致這些屬性為null,而Gson默認的規(guī)則不會解析為null的屬性，比如：
public String getEndTime() {
if (this.endTime == null) {
Date endDate = (null == historicProcessInstance) ? null : historicProcessInstance.getEndTime();
endTime = endDate == null ? "" : DateFormatUtil.format(endDate);
}
return endTime;
}
(3)換解析方式：使用FastJson。
因為FastJson是通過getter方法獲取屬性，并把其值序列化成json字符串的，所以這里，我們這個實體類中去掉不想被解析的屬性的get方法，變成如下：
public void setTask(Task task) {
this.task = task;
}
public void setProcessInstance(ProcessInstance processInstance) {
this.processInstance = processInstance;
}
public void setHistoricProcessInstance(HistoricProcessInstance historicProcessInstance) {
this.historicProcessInstance = historicProcessInstance;
}
public void setProcessDefinition(ProcessDefinition processDefinition) {
this.processDefinition = processDefinition;
}
public void setHistoricTaskInstance(HistoricTaskInstance historicTaskInstance) {
this.historicTaskInstance = historicTaskInstance;
}
