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java json转换

發(fā)布時(shí)間：2025/7/14 编程问答 17 豆豆

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https://blog.csdn.net/WillJGL/article/details/77866224

SpringBoot中如果需要實(shí)現(xiàn)json的序列化和反序列化，我們會(huì)使用json解析工具。一般用到的有fastjson、GSON、Jackson
根據(jù)網(wǎng)上的測(cè)試，Jackson性能好一些，而且Jackson是SpringBoot默認(rèn)引用的
本文記錄SpringBoot如何使用Jackson

準(zhǔn)備

1、在項(xiàng)目中創(chuàng)建包Jackson
2、分別創(chuàng)建4各類(lèi)文件
2.1、Company實(shí)體類(lèi)（里面包含Department的list）
2.2、Department實(shí)體類(lèi)
2.3、jsonController controller類(lèi)，接收測(cè)試請(qǐng)求
2.4、JsonHelper Jackson操作類(lèi)
如題所示

每個(gè)類(lèi)內(nèi)容如下
Company

import java.util.ArrayList; import java.util.List;public class Company { private String name; private String address; private int employeesCount; private List<Department> departmentArrayList; public String getName() { return name; } public void setName(String name) { this.name = name; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } public int getEmployeesCount() { return employeesCount; } public void setEmployeesCount(int employeesCount) { this.employeesCount = employeesCount; } public List<Department> getDepartmentArrayList() { return departmentArrayList; } public void setDepartmentArrayList(List<Department> departmentArrayList) { this.departmentArrayList = departmentArrayList; } }

Department

public class Department {private String name;private int employeesCount; public String getName() { return name; } public void setName(String name) { this.name = name; } public int getEmployeesCount() { return employeesCount; } public void setEmployeesCount(int employeesCount) { this.employeesCount = employeesCount; } }

jsonController

import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.core.type.TypeReference; import com.fasterxml.jackson.databind.JavaType; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import java.util.*; @RestController @RequestMapping("/json") public class jsonController { private final Logger logger = LoggerFactory.getLogger(this.getClass());//對(duì)象方式初始化Log對(duì)象 @GetMapping("") public String index() throws Exception { JsonHelper jm = new JsonHelper(); //1、對(duì)象<->Json //準(zhǔn)備數(shù)據(jù) Company c = getCompany(); //對(duì)象轉(zhuǎn)Json String json = jm.toJson(c); logger.info("1.1、對(duì)象轉(zhuǎn)Json="+json); //Json轉(zhuǎn)對(duì)象 Company obj = jm.fromJson(json,Company.class); logger.info("1.2、Json轉(zhuǎn)對(duì)象="+ obj.getDepartmentArrayList().get(0).getName()); //2、Map<->Json //Json轉(zhuǎn)Map Map map = jm.fromJson(json,Map.class); List<Map> tempList = (List<Map>)map.get("departmentArrayList"); logger.info("2.1、Json轉(zhuǎn)Map="+tempList.get(0).get("name")); //Map轉(zhuǎn)Json json = jm.toJson(map); logger.info("2.2、Map轉(zhuǎn)Json="+json); //3、List<Object> <->Json //準(zhǔn)備數(shù)據(jù) List<Company> companyList = new ArrayList<Company>(); companyList.add(getCompany()); companyList.add(getCompany()); companyList.add(getCompany()); //List<Object>轉(zhuǎn)Json json = jm.toJson(companyList); logger.info("3.1、List<Object>轉(zhuǎn)Json="+json); //Json轉(zhuǎn)List<Object> List<Company> companyListDecode = jm.fromJson(json,new TypeReference<List<Company>>() {}); logger.info("3.2、Json轉(zhuǎn)List<Object>="+companyListDecode.get(0).getDepartmentArrayList().get(0).getName()); //4、Map<String, Object><-> Json //準(zhǔn)備數(shù)據(jù) Map<String, Company> map1 = new HashMap<String, Company>() ; map1.put("1",getCompany()); map1.put("2",getCompany()); map1.put("3",getCompany()); //Map<String, Object>轉(zhuǎn)Json json = jm.toJson(map1); logger.info("4.1、Map<String, Object>轉(zhuǎn)Json="+json); //Json轉(zhuǎn)Map<String, Object> Map<String, Company> map1Decode = jm.fromJson(json,new TypeReference<Map<String, Company>>() {}); logger.info("4.2、Json轉(zhuǎn)Map<String, Object>="+map1Decode.get("1").getDepartmentArrayList().get(0).getName()); //5、List<Map<String, Object>><->Json //準(zhǔn)備數(shù)據(jù) List<Map<String, Company>> listMap =new ArrayList<Map<String, Company>>(); Map<String, Company> map2 = new HashMap<String, Company>() ; map2.put("a",getCompany()); map2.put("b",getCompany()); map2.put("c",getCompany()); listMap.add(map1); listMap.add(map2); //List<Map<String, Object>> 轉(zhuǎn)Json json = jm.toJson(listMap); logger.info("5.1、List<Map<String, Object>> 轉(zhuǎn)Json="+json); //Json 轉(zhuǎn) List<Map<String, Object>> List<Map<String, Company>> listMapDecode = jm.fromJson(json,new TypeReference<List<Map<String, Company>>>() {}); logger.info("5.2、List<Map<String, Object>> 轉(zhuǎn)Json="+listMapDecode.get(0).get("1").getDepartmentArrayList().get(0).getName()); return ""; } private Company getCompany() { long time = new Date().getTime(); String sTime = String.valueOf(time); Company c = new Company(); c.setEmployeesCount(10); c.setName("公司名"+sTime); List list = new ArrayList(); Department d1= new Department(); d1.setEmployeesCount(5); d1.setName("部門(mén)1"+sTime); Department d2= new Department(); d2.setEmployeesCount(5); d2.setName("部門(mén)2"+sTime); list.add(d1); list.add(d2); c.setDepartmentArrayList(list); return c; } }

JsonHelper

import com.fasterxml.jackson.annotation.JsonInclude; import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.core.type.TypeReference; import com.fasterxml.jackson.databind.DeserializationFeature; import com.fasterxml.jackson.databind.JavaType; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.SerializationFeature; import com.fasterxml.jackson.databind.util.JSONPObject; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.io.IOException; public class JsonHelper { private Logger logger = LoggerFactory.getLogger(this.getClass()); ObjectMapper mapper; public JsonHelper() { mapper = new ObjectMapper(); mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL); mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false); } public JsonHelper(JsonInclude.Include include) { mapper = new ObjectMapper(); mapper.setSerializationInclusion(include); mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false); } public String toJson(Object object) throws JsonProcessingException { return mapper.writeValueAsString(object); } public <T> T fromJson(String json, Class<T> cls) throws IOException { return mapper.readValue(json, cls); } public <T> T fromJson(String json,TypeReference valueTypeRef) throws IOException { return mapper.readValue(json, valueTypeRef); } }

轉(zhuǎn)換方式

共舉例如下幾種轉(zhuǎn)換方式（整體在jsonController文件中，這里分別拆出來(lái)說(shuō)明）

對(duì)象<->Json

//1、對(duì)象<->Json//準(zhǔn)備數(shù)據(jù)Company c = getCompany();//對(duì)象轉(zhuǎn)JsonString json = jm.toJson(c); logger.info("1.1、對(duì)象轉(zhuǎn)Json="+json); //Json轉(zhuǎn)對(duì)象 Company obj = jm.fromJson(json,Company.class); logger.info("1.2、Json轉(zhuǎn)對(duì)象="+ obj.getDepartmentArrayList().get(0).getName());

Map<->Json

//2、Map<->Json//Json轉(zhuǎn)MapMap map = jm.fromJson(json,Map.class); List<Map> tempList = (List<Map>)map.get("departmentArrayList"); logger.info("2.1、Json轉(zhuǎn)Map="+tempList.get(0).get("name")); //Map轉(zhuǎn)Json json = jm.toJson(map); logger.info("2.2、Map轉(zhuǎn)Json="+json);

List<Object> <->Json

//3、List<Object> <->Json//準(zhǔn)備數(shù)據(jù)List<Company> companyList = new ArrayList<Company>();companyList.add(getCompany()); companyList.add(getCompany()); companyList.add(getCompany()); //List<Object>轉(zhuǎn)Json json = jm.toJson(companyList); logger.info("3.1、List<Object>轉(zhuǎn)Json="+json); //Json轉(zhuǎn)List<Object> List<Company> companyListDecode = jm.fromJson(json,new TypeReference<List<Company>>() {}); logger.info("3.2、Json轉(zhuǎn)List<Object>="+companyListDecode.get(0).getDepartmentArrayList().get(0).getName());

Map<String, Object><-> Json

//4、Map<String, Object><-> Json//準(zhǔn)備數(shù)據(jù)Map<String, Company> map1 = new HashMap<String, Company>() ; map1.put("1",getCompany()); map1.put("2",getCompany()); map1.put("3",getCompany()); //Map<String, Object>轉(zhuǎn)Json json = jm.toJson(map1); logger.info("4.1、Map<String, Object>轉(zhuǎn)Json="+json); //Json轉(zhuǎn)Map<String, Object> Map<String, Company> map1Decode = jm.fromJson(json,new TypeReference<Map<String, Company>>() {}); logger.info("4.2、Json轉(zhuǎn)Map<String, Object>="+map1Decode.get("1").getDepartmentArrayList().get(0).getName());

List<Map<String, Object>><->Json

//5、List<Map<String, Object>><->Json //準(zhǔn)備數(shù)據(jù) List<Map<String, Company>> listMap =new ArrayList<Map<String, Company>>(); Map<String, Company> map2 = new HashMap<String, Company>() ; map2.put("a",getCompany()); map2.put("b",getCompany()); map2.put("c",getCompany()); listMap.add(map1); listMap.add(map2); //List<Map<String, Object>> 轉(zhuǎn)Json json = jm.toJson(listMap); logger.info("5.1、List<Map<String, Object>> 轉(zhuǎn)Json="+json); //Json 轉(zhuǎn) List<Map<String, Object>> List<Map<String, Company>> listMapDecode = jm.fromJson(json,new TypeReference<List<Map<String, Company>>>() {}); logger.info("5.2、List<Map<String, Object>> 轉(zhuǎn)Json="+listMapDecode.get(0).get("1").getDepartmentArrayList().get(0).getName());

測(cè)試

訪問(wèn)controller的方法，查看日志可以看出來(lái)每種轉(zhuǎn)換都可以成功轉(zhuǎn)為json，也可以成功轉(zhuǎn)為對(duì)象

其它特性

在有些時(shí)候，我們會(huì)希望進(jìn)行一些特殊處理，例如json不

忽略字段

@JsonIgnore 進(jìn)行JSON操作時(shí)忽略該屬性。
對(duì)于實(shí)體類(lèi)中，如果有某個(gè)字段不希望參與json序列化與反序列化，可以把屬性標(biāo)記為@JsonIgnore
例如Company這個(gè)類(lèi)
如果我們給Name、Address、employeesCount三個(gè)屬性賦值了，序列化出來(lái)的內(nèi)容是

{"name": "公司名1504688970821", "address": "地址", "employeesCount": 10 }

如果employeesCount是一個(gè)內(nèi)容計(jì)數(shù)的值，不希望參與序列化，我們可以標(biāo)記它

@JsonIgnoreprivate int employeesCount;

這樣再次序列化的結(jié)果就變?yōu)榱?/span>

{"name": "公司名1504689048950", "address": "地址" }

處理時(shí)間類(lèi)型

@JsonFormat(pattern = “yyyy年MM月dd日”) 時(shí)間格式化
我們?cè)贑ompany實(shí)體類(lèi)增加一個(gè)Date類(lèi)型的屬性，并且賦值序列化

private Date createDate;public Date getCreateDate() {return createDate; } public void setCreateDate(Date createDate) { this.createDate = createDate; }

賦值然后再序列化，得到的內(nèi)容是

{"name": "公司名1504689283756", "address": "地址", "createDate": 1504689283756 }

可以看到時(shí)間是一個(gè)數(shù)字
我們標(biāo)記這個(gè)屬性，再次序列化

{"name": "公司名1504689362487", "address": "地址", "createDate": "2017年09月06日" }

時(shí)間按照指定的格式顯示了

更改字段序列化名

@JsonProperty(“newName”) 改字段名
默認(rèn)情況下，字段名是什么，序列化出來(lái)的key值也就是什么，如果我們希望序列化出來(lái)的名字和字段名不一樣，則需要使用這個(gè)標(biāo)記
我們把Company的name標(biāo)記為newName

@JsonProperty("newName")private String name;

然后進(jìn)行序列化

{"address": "地址", "createDate": "2017年09月06日", "newName": "公司名1504689496978" }

可以看出來(lái)，結(jié)果出來(lái)的key就使用了自定義的名字

總結(jié)

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