ObjectMapper 忽略字段大小写
核心代码:
- ObjectMapper mapper = new ObjectMapper();
- mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
- mapper.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true);
例子:
- import com.fasterxml.jackson.databind.DeserializationFeature;
- import com.fasterxml.jackson.databind.JsonMappingException;
- import com.fasterxml.jackson.databind.MapperFeature;
- import com.fasterxml.jackson.databind.ObjectMapper;
- public class Test{
- public static void main(String[] args) {
- try {
- A a = new A();
- a.lastname = "jack";
- ObjectMapper mapper = new ObjectMapper();
- mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
- mapper.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true);
- A2 convertValue = new A2();
- mapper.updateValue(convertValue, a);
- System.out.println(convertValue);
- } catch (JsonMappingException e) {
- e.printStackTrace();
- }
- }
- public static class A{
- String lastname;
- public String getLastname() {
- return lastname;
- }
- public void setLastname(String lastname) {
- this.lastname = lastname;
- }
- }
- public static class A2{
- String lastName;
- public String getLastName() {
- return lastName;
- }
- public void setLastName(String lastName) {
- this.lastName = lastName;
- }
- @Override
- public String toString() {
- return "A2 [lastName=" + lastName + "]";
- }
- }
- }
ObjectMapper 的一些坑
相信做过Java 开发对这个类应该不陌生,没错,这个类是jackson提供的,主要是用来把对象转换成为一个json字符串返回到前端,
现在大部分数据交换都是以json来传输的,所以这个很重要,那你到底又对这个类有着有多少了解呢,下面我说一下我遇到的一些坑
首先,先把我要说的几个坑需要设置的属性贴出来先
- ObjectMapper objectMapper = new ObjectMapper();
- //序列化的时候序列对象的所有属性
- objectMapper.setSerializationInclusion(Include.ALWAYS);
- //反序列化的时候如果多了其他属性,不抛出异常
- objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
- //如果是空对象的时候,不抛异常
- objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
- //取消时间的转化格式,默认是时间戳,可以取消,同时需要设置要表现的时间格式
- objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
- objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"))
简单说一下这个类的基本用法,以下采用代码块加截图的形式来说明和部分文字件数
- package com.shiro.test;
- import java.text.SimpleDateFormat;
- import java.util.Date;
- import com.fasterxml.jackson.annotation.JsonInclude.Include;
- import com.fasterxml.jackson.databind.DeserializationFeature;
- import com.fasterxml.jackson.databind.ObjectMapper;
- import com.fasterxml.jackson.databind.SerializationFeature;
- public class Main2 {
- public static void main(String[] args) throws Exception{
- ObjectMapper objectMapper = new ObjectMapper();
- //序列化的时候序列对象的所有属性
- objectMapper.setSerializationInclusion(Include.ALWAYS);
- //取消时间的转化格式,默认是时间戳,可以取消,同时需要设置要表现的时间格式
- objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
- objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
- Person person = new Person(1, "zxc", new Date());
- //这是最简单的一个例子,把一个对象转换为json字符串
- String personJson = objectMapper.writeValueAsString(person);
- System.out.println(personJson);
- //默认为true,会显示时间戳
- objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, true);
- personJson = objectMapper.writeValueAsString(person);
- System.out.println(personJson);
- }
- }
输出的信息如下
objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false)的作用
- package com.shiro.test;
- import java.text.SimpleDateFormat;
- import java.util.Date;
- import com.fasterxml.jackson.annotation.JsonInclude.Include;
- import com.fasterxml.jackson.databind.DeserializationFeature;
- import com.fasterxml.jackson.databind.ObjectMapper;
- import com.fasterxml.jackson.databind.SerializationFeature;
- public class Main2 {
- public static void main(String[] args) throws Exception{
- ObjectMapper objectMapper = new ObjectMapper();
- //序列化的时候序列对象的所有属性
- objectMapper.setSerializationInclusion(Include.ALWAYS);
- //如果是空对象的时候,不抛异常,也就是对应的属性没有get方法
- objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
- Person person = new Person(1, "zxc", new Date());
- String personJson = objectMapper.writeValueAsString(person);
- System.out.println(personJson);
- //默认是true,即会抛异常
- objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, true);
- personJson = objectMapper.writeValueAsString(person);
- System.out.println(personJson);
- }
- }
对应的person类此时为
- package com.shiro.test;
- import java.util.Date;
- public class Person {
- private Integer id;
- private String name;
- private Date birthDate;
- // public Integer getId() {
- // return id;
- // }
- // public void setId(Integer id) {
- // this.id = id;
- // }
- // public String getName() {
- // return name;
- // }
- // public void setName(String name) {
- // this.name = name;
- // }
- // public Date getBirthDate() {
- // return birthDate;
- // }
- // public void setBirthDate(Date birthDate) {
- // this.birthDate = birthDate;
- // }
- @Override
- public String toString() {
- return "Person [id=" + id + ", name=" + name + ", birthDate=" + birthDate + "]";
- }
- public Person(Integer id, String name, Date birthDate) {
- super();
- this.id = id;
- this.name = name;
- this.birthDate = birthDate;
- }
- public Person() {
- // TODO Auto-generated constructor stub
- }
- }
结果如下
- package com.shiro.test;
- import com.fasterxml.jackson.annotation.JsonInclude.Include;
- import com.fasterxml.jackson.databind.DeserializationFeature;
- import com.fasterxml.jackson.databind.ObjectMapper;
- public class Main2 {
- public static void main(String[] args) throws Exception{
- ObjectMapper objectMapper = new ObjectMapper();
- //序列化的时候序列对象的所有属性
- objectMapper.setSerializationInclusion(Include.ALWAYS);
- //反序列化的时候如果多了其他属性,不抛出异常
- objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
- // Person person = new Person(1, "zxc", new Date());
- // String personJson = objectMapper.writeValueAsString(person);
- // System.out.println(personJson);
- //注意,age属性是不存在在person对象中的
- String personStr = "{\"id\":1,\"name\":\"zxc\",\"age\":\"zxc\"}";
- Person person = objectMapper.readValue(personStr, Person.class);
- System.out.println(person);
- //默认为true
- objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, true);
- person = objectMapper.readValue(personStr, Person.class);
- System.out.println(person);
- }
- }
执行后的结果如下
这些便是这几个属性的作用所以,由于第一个比较简单我就这样说一下吧
Include.ALWAYS 是序列化对像所有属性
Include.NON_NULL 只有不为null的字段才被序列化
Include.NON_EMPTY 如果为null或者 空字符串和空集合都不会被序列化
然后再说一下如何把一个对象集合转换为一个 Java里面的数组
- package com.shiro.test;
- import java.util.ArrayList;
- import java.util.Date;
- import java.util.List;
- import com.fasterxml.jackson.annotation.JsonInclude.Include;
- import com.fasterxml.jackson.core.type.TypeReference;
- import com.fasterxml.jackson.databind.JavaType;
- import com.fasterxml.jackson.databind.ObjectMapper;
- public class Main2 {
- public static void main(String[] args) throws Exception{
- ObjectMapper objectMapper = new ObjectMapper();
- //序列化的时候序列对象的所有属性
- objectMapper.setSerializationInclusion(Include.NON_DEFAULT);
- Person person1 = new Person(1, "zxc", new Date());
- Person person2 = new Person(2, "ldh", new Date());
- List<Person> persons = new ArrayList<>();
- persons.add(person1);
- persons.add(person2);
- //先转换为json字符串
- String personStr = objectMapper.writeValueAsString(persons);
- //反序列化为List<user> 集合,1需要通过 TypeReference 来具体传递值
- List<Person> persons2 = objectMapper.readValue(personStr, new TypeReference<List<Person>>() {});
- for(Person person : persons2) {
- System.out.println(person);
- }
- //2,通过 JavaType 来进行处理返回
- JavaType javaType = objectMapper.getTypeFactory().constructParametricType(List.class, Person.class);
- List<Person> persons3 = objectMapper.readValue(personStr, javaType);
- for(Person person : persons3) {
- System.out.println(person);
- }
- }
- }
以上为个人经验,希望能给大家一个参考,也希望大家多多支持我们。
原文链接:https://blog.csdn.net/weixin_42713970/article/details/88061100