本篇内容主要讲解“ObjectMapper怎么忽略字段大小写”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“ObjectMapper怎么忽略字段大小写”吧!
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;//}@Overridepublic 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trueobjectMapper.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);}}}到此，相信大家对“ObjectMapper怎么忽略字段大小写”有了更深的了解，不妨来实际操作一番吧！这里是编程网网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！
