java~jackson实现接口的反序列化

jackson是springboot中集成的序列化方式，是默认的json序列化方式，当然你可以使用其它的序列化工具代替它，不过今天我们还是说一下它，使用jackson进行序列化一个类，然后再把它的JSON字符反序列化为它的接口对象。

现实

1. 这种方式默认是不行的，因为接口不能被自动实例化
2. 使用redisTelmplete时，如果使用objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);这种试序列化，由于会把实例类型写到时 JSON里，所以也不能反序列化为接口

几个序列化方式

一 序列化为具体类型，无法反序列化接口，即你用什么类型序列化的，就用什么类型反序列化，它经常与redis的序列化Jackson2JsonRedisSerializer一起使用。

        ObjectMapper om = new ObjectMapper();
        om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        User user = new User();
        user.setUsername("lind");
        user.setEmail("zzl@sina.com");
        String msg = om.writeValueAsString(user);

结果

["com.lind.common.JacksonTest$User",{"username":"lind","email":"zzl@sina.com","authorities":null}]

二 序列化为字符串，主要好处是与类型无关，只要字段可以配置上，就可以反序列化，并且在自定义序列化器定义之后，还可以对接口类型进行反序列化，可以说更加方便。
定义一个序列化器

 public static class DefaultResourceUserSerializer extends JsonDeserializer<DefaultResourceUser> {

        @Override
        public DefaultResourceUser deserialize(JsonParser jsonParser, DeserializationContext deserializationContext)
                throws IOException {
            ObjectCodec oc = jsonParser.getCodec();
            JsonNode node = oc.readTree(jsonParser);
            DefaultResourceUser userAccountAuthentication = new DefaultResourceUser() {
                @Override
                public String getUsername() {
                    return node.get("username").asText();
                }

                @Override
                public String getEmail() {
                    return node.get("email").asText();
                }

                @Override
                public Collection<? extends GrantedAuthority> getAuthorities() {
                    List<GrantedAuthority> simpleGrantedAuthorities = new ArrayList<>();
                    Iterator<JsonNode> elements = node.get("authorities").elements();
                    while (elements.hasNext()) {
                        JsonNode next = elements.next();
                        JsonNode authority = next.get("authority");
                        simpleGrantedAuthorities.add(new SimpleGrantedAuthority(authority.asText()));
                    }
                    return simpleGrantedAuthorities;
                }
            };
            return userAccountAuthentication;
        }

在接口上使用它
``java
@JsonDeserialize(using = DefaultResourceUserSerializer.class)
public interface DefaultResourceUser {
String getUsername();

    String getEmail();

    Collection<? extends GrantedAuthority> getAuthorities();
}

代码展现了反序列化一个json字符串
```json
{
  "id": "347214418355949568",
  "username": "admin",
  "password": "{bcrypt}$2a$10$tVrm4VjC9BXF8PStUASZkOJCOm7mKR4ZVDHau.Ug/tm6ZEXEsHhcC",
  "nickName": "测试",
  "mobile": "",
  "email": "",
  "address": "北京",
  "street": "",
  "sex": 0,
  "passStrength": "",
  "avatar": "",
  "type": 0,
  "status": 0,
  "description": "",
  "departmentId": "",
  "departmentTitle": null,
  "resourcePermissions": [{
    "id": "348193374957735936",
    "title": "系统管理",
    "path": "",
    "type": 0,
    "parentId": "",
    "parent": null,
    "sons": null
  }, {
    "id": "348193687223668737",
    "title": "用户管理",
    "path": "/user",
    "type": 0,
    "parentId": "348193374957735936",
    "parent": null,
    "sons": null
  }, {
    "id": "348193868908335105",
    "title": "添加用户",
    "path": "/user/add*",
    "type": 0,
    "parentId": "348193687223668737",
    "parent": null,
    "sons": null
  }, {
    "id": "348193927590842369",
    "title": "用户列表",
    "path": "/user/list*",
    "type": 0,
    "parentId": "348193687223668737",
    "parent": null,
    "sons": null
  }, {
    "id": "348194428344602626",
    "title": "权限管理",
    "path": "/permission/**",
    "type": 0,
    "parentId": "348193374957735936",
    "parent": null,
    "sons": null
  }, {
    "id": "348194428344602627",
    "title": "权限添加",
    "path": "/permission/add*",
    "type": 0,
    "parentId": "348194428344602626",
    "parent": null,
    "sons": null
  }, {
    "id": "348194428344602628",
    "title": "角色管理",
    "path": "/role/list",
    "type": 0,
    "parentId": "348193374957735936",
    "parent": null,
    "sons": null
  }, {
    "id": "348194428344602629",
    "title": "demo",
    "path": "/demo",
    "type": 0,
    "parentId": "348193374957735936",
    "parent": null,
    "sons": null
  }],
  "resourceRoles": null,
  "enabled": true,
  "authorities": [{
    "authority": "用户管理"
  }, {
    "authority": "添加用户"
  }, {
    "authority": "用户列表"
  }, {
    "authority": "权限管理"
  }, {
    "authority": "权限添加"
  }, {
    "authority": "角色管理"
  }, {
    "authority": "demo"
  }],
  "accountNonLocked": true,
  "accountNonExpired": true,
  "credentialsNonExpired": true
}

代码

    @SneakyThrows
    @Test
    public void stringJackson() {
        DefaultResourceUser user = fromJson("jack.json", DefaultResourceUser.class);
        log.info("user:{}", user.getUsername());
        for (GrantedAuthority grantedAuthority : user.getAuthorities()) {
            log.info("auth:{}", grantedAuthority.getAuthority());
        }

    }

结果

1