ObjectMapper类 _ObjectMapper

案头见蠹鱼，犹胜凡俦侣。这篇文章主要讲述ObjectMapper类相关的知识，希望能为你提供帮助。
前言ObjectMapper类是Jackson库的主要类。它提供一些功能将转换成java对象匹配JSON结构，反之亦然
使用使用Jackson，首先需要相关的jar包。对于使用maven的，需要添加以下依赖：

< !-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind --> < dependency> < groupId> com.fasterxml.jackson.core< /groupId> < artifactId> jackson-databind< /artifactId> < version> 2.9.5< /version> < /dependency> < !-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core --> < dependency> < groupId> com.fasterxml.jackson.core< /groupId> < artifactId> jackson-core< /artifactId> < version> 2.9.5< /version> < /dependency> < !-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations --> < dependency> < groupId> com.fasterxml.jackson.core< /groupId> < artifactId> jackson-annotations< /artifactId> < version> 2.9.5< /version> < /dependency>

实例演示 Java对象转换为JSON对象 json对象转化为java 对象

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"))

PS：还需要注意，如果ObjectMapper的configure设置FAIL_ON_EMPTY_BEANS为false，那么对应的实体类的属性没有get方法也不会抛出异常，但是这个属性默认的是true，即必须要有get方法，这个需要注意。

public class ObjectMapperTest {public static void main(String[] args) throws IOException {ObjectMapper objectMapper = new ObjectMapper(); objectMapper.setSerializationInclusion(JsonInclude.Include.ALWAYS); objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, true); Person person = new Person(1, "tom", "123"); String jsonString = objectMapper.writeValueAsString(person); System.out.println("JsonString: " + jsonString); Person person1 = objectMapper.readValue(jsonString, Person.class); System.out.println(person1.toString()); }}

Java数组对象和JSON数组对象之间的转换

public static void getListData() { ObjectMapper objectMapper = new ObjectMapper(); //Java数组转换为JSON数组 Person person = new Person(1, "tom", "123"); Person person1 = new Person(2, "jack", "123445"); List< Person> personList = new ArrayList< > (); personList.add(person); personList.add(person1); String jsonString = null; try { //Json数组转换为Java数组 jsonString = objectMapper.writeValueAsString(personList); System.out.println("JsonString List: " + jsonString); //JavaType JavaType javaType = objectMapper.getTypeFactory().constructParametricType(List.class, Person.class); List< Person> list = objectMapper.readValue(jsonString, javaType); //打印出list中的值 for (Person person2 : list) { System.out.println(person2.toString()); } } catch (Exception e) { e.printStackTrace(); } }

【ObjectMapper类】