ObjectMapper 如何忽略字段大小写

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

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