使用Jackson实现Map与Bean互转方式_Java教程

Jackson Map与Bean互转

在使用 java 开发中，通常需要把 Map 转成 Bean，或把 Bean 转成 Map，这就用的工具类，在此推荐使用import com.fasterxml.jackson.databind.ObjectMapper;包下的ObjectMapper类，比 JsonObject 效率高

下面就列举了几种使用方法

1、pom.xml

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									<dependency>

									    <groupId>com.fasterxml.jackson.core</groupId>

									    <artifactId>jackson-databind</artifactId>

									    <version>2.9.6</version>

									    <scope>compile</scope>

									</dependency>

2、java 代码

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									package com.jin.demo.jackson;

									import com.fasterxml.jackson.databind.ObjectMapper;

									import java.util.HashMap;

									import java.util.Map;

									/**

									 * 使用 Jackson工具

									 * map to bean

									 * bean to map

									 *

									 * @auther jinsx

									 * @date 2019-03-26 16:37

									 */

									public class JacksonTest {

									    private static final ObjectMapper mapper = new ObjectMapper();

									    public static void main(String[] args) throws Exception {

									        // 测试 将Map转成指定的Bean

									        Map<String, Object> map = new HashMap<>();

									        map.put("name", "张三");

									        Person o = (Person)JacksonTest.mapToBean(map, Person.class);

									        System.out.println(o);

									        // 测试 将Bean转成Map

									        Person person = new Person();

									        person.setAge(18);

									        Map map1 = JacksonTest.beanToMap(person);

									        System.out.println(map1);

									    }

									    // 将对象转成字符串

									    public static String objectToString(Object obj) throws Exception {

									        return mapper.writeValueAsString(obj);

									    }

									    // 将Map转成指定的Bean

									    public static Object mapToBean(Map map, Class clazz) throws Exception {

									        return mapper.readValue(objectToString(map), clazz);

									    }

									    // 将Bean转成Map

									    public static Map beanToMap(Object obj) throws Exception {

									        return mapper.readValue(objectToString(obj), Map.class);

									    }

									}

3、Person 类

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									package com.jin.demo.jackson;

									import java.io.Serializable;

									import java.util.Date;

									/**

									 * @auther jinsx

									 * @date 2019-03-26 17:30

									 */

									public class Person implements Serializable {

									    private int age;

									    private String name;

									    private Date birthday;

									    public int getAge() {

									        return age;

									    }

									    public void setAge(int age) {

									        this.age = age;

									    }

									    public String getName() {

									        return name;

									    }

									    public void setName(String name) {

									        this.name = name;

									    }

									    public Date getBirthday() {

									        return birthday;

									    }

									    public void setBirthday(Date birthday) {

									        this.birthday = birthday;

									    }

									    @Override

									    public String toString() {

									        return "Person{" +

									                "age=" + age +

									                ", name='" + name + '\'' +

									                ", birthday=" + birthday +

									                '}';

									    }

									}

Jackson-ObjectMapper json字符串、bean、map、list互相转换

1、对象转json字符串

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									ObjectMapper mapper = new ObjectMapper();

									User user = new User();

									String userJson = mapper.writeValueAsString(user);

2、Map转json字符串

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									ObjectMapper mapper = new ObjectMapper();

									Map map = new HashMap();

									String json = mapper.writeValueAsString(map);

3、数组list转json字符串

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									ObjectMapper mapper = new ObjectMapper();

									User[] uArr = {user1, user2};

									String jsonfromArr = mapper.writeValueAsString(uArr);

4、json字符串转对象

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									ObjectMapper mapper = new ObjectMapper();

									String expected = "{\"name\":\"ZhangSan\"}";

									User user = mapper.readValue(expected, User.class);

5、json字符串转Map

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									ObjectMapper mapper = new ObjectMapper();

									String expected = "{\"name\":\"ZhangSan\"}";

									Map userMap = mapper.readValue(expected, Map.class);

6、json字符串转对象数组List

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									ObjectMapper mapper = new ObjectMapper();

									String expected = "[{\"name\":\"Zhangsan\"},{\"name\":\"Lisi\"}]";

									CollectionType listType = mapper.getTypeFactory().constructCollectionType(ArrayList.class, User.class);

									List<User> userList = mapper.readValue(expected, listType);

7、json字符串转Map数组List<Map<String,Object>>

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									ObjectMapper mapper = new ObjectMapper();

									String expected = "[{\"name\":\"Zhangsan\"},{\"nameEn\":\"Lisi\"}]";

									CollectionType listType = mapper.getTypeFactory().constructCollectionType(ArrayList.class, Map.class);

									List<Map<String,Object>> userList = mapper.readValue(expected, listType);

8、jackson默认将对象转换为LinkedHashMap

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									ObjectMapper mapper = new ObjectMapper();

									String expected = "[{\"name\":\"Zhangsan\"},{\"nameEn\":\"Lisi\"},{\"name\":\"Test\"}]";

									ArrayList arrayList = mapper.readValue(expected, ArrayList.class);

9、json字符串转对象设置格式

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									ObjectMapper mapper = new ObjectMapper();

									//设置date转换格式

									SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

									mapper.setDateFormat(fmt);

									String expected = "{\"name\":\"ZhangSan\",\"bir\":\"2021-04-15 14:00:00\"}";

									User user = mapper.readValue(expected, User.class);

10、忽略未知字段

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									ObjectMapper mapper = new ObjectMapper();

									//设置忽略未知字段

									mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

									String expected = "{\"name\":\"ZhangSan\",\"job\":\"teacher\"}";

									User user = mapper.readValue(expected, User.class);