ObjectMapper 如何忽略字段大小写
ObjectMapper 如何忽略字段大小写
这篇文章主要介绍了使用ObjectMapper实现忽略字段大小写操作,具有很好的参考价值,希望对大家有所帮助。如有错误或未考虑完全的地方,望不吝赐教
ObjectMapper 忽略字段大小写
核心代码:
1 2 3 | ObjectMapper mapper = new ObjectMapper(); mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false ); mapper.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true ); |
例子:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 | 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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | 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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 | 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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | 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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 | 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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 | 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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | 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脚本之家。
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原文链接:https://blog.csdn.net/weixin_42713970/article/details/88061100