fastjson和jackson使用对比

标签：parser   编写   static   figure   ack   结果   png   row   code   

介绍

Fastjson是一个Java语言编写的高性能的JSON处理器,由阿里巴巴公司开发。无依赖，不需要例外额外的jar，能够直接跑在JDK上。 FastJson在复杂类型的Bean转换Json上会出现一些问题，可能会出现引用的类型，导致Json转换出错，需要制定引用。 FastJson采用独创的算法，将parse的速度提升到极致，超过所有json库。
Jackson是当前用的比较广泛的，用来序列化和反序列化json的Java开源框架。Jackson社区相对比较活跃，更新速度也比较快， 从Github中的统计来看，Jackson是最流行的json解析器之一，Spring MVC的默认json解析器便是Jackson。

添加maven依赖

<!--fastjson依赖-->
<dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>fastjson</artifactId>
      <version>1.2.56</version>
 </dependency>
<!--jackson依赖-->
 <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.9.4</version>
</dependency>
<dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-annotations</artifactId>
      <version>2.9.4</version>
</dependency>

将java bean序列化为json字符串

过滤null值

public class Client1 {

  public static void main(String[] args) {
    User user = new User();
    user.setUsername("lisi");
    System.out.println(JSON.toJSONString(user));
  }

  @Setter
  @Getter
  static class User {

    private String username;
    private String password;
  }
}

fastjson将javabean转成字符串，结果为：{"username":"lisi"}，默认过滤null值

public class Client2 {

  public static void main(String[] args) throws JsonProcessingException {
    User user = new User();
    user.setUsername("lisi");
    ObjectMapper objectMapper = new ObjectMapper();
    //只包含非null值
    objectMapper.setSerializationInclusion(Include.NON_NULL);
    System.out.println(objectMapper.writeValueAsString(user));
  }

  @Setter
  @Getter
  static class User {

    private String username;
    private String password;
  }
}

jackson默认保留null值

保留null值

如果不想过滤，fastjson可以使用以下方式

public class Client1 {

  public static void main(String[] args) {
    User user = new User();
    user.setUsername("lisi");
    //保留null值
    System.out.println(JSON.toJSONString(user, SerializerFeature.WriteMapNullValue));
  }

  @Setter
  @Getter
  static class User {

    private String username;
    private String password;
  }
}

结果为：{"password":null,"username":"lisi"}

public class Client2 {

  public static void main(String[] args) throws JsonProcessingException {
    User user = new User();
    user.setUsername("lisi");
    ObjectMapper objectMapper = new ObjectMapper();
    System.out.println(objectMapper.writeValueAsString(user));
  }

  @Setter
  @Getter
  static class User {

    private String username;
    private String password;
  }
}

jackson默认就是保留null值

美化显示

public class Client1 {

  public static void main(String[] args) {
    User user = new User();
    user.setUsername("lisi");
    //保留null值，字符串格式化方式显示
    System.out.println(JSON.toJSONString(user, SerializerFeature.WriteMapNullValue,
        SerializerFeature.PrettyFormat));
  }

  @Setter
  @Getter
  static class User {

    private String username;
    private String password;
  }
}

public class Client2 {

  public static void main(String[] args) throws JsonProcessingException {
    User user = new User();
    user.setUsername("lisi");
    ObjectMapper objectMapper = new ObjectMapper();
    System.out.println(objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(user));
  }

  @Setter
  @Getter
  static class User {

    private String username;
    private String password;
  }
}

输出为：

{
	"password":null,
	"username":"lisi"
}

忽略属性和属性别名

public class Client1 {

  public static void main(String[] args) {
    User user = new User();
    user.setOpenId("lisi");
    user.setPassword("123456");
    System.out.println(JSON.toJSONString(user));
  }

  @Setter
  @Getter
  @ToString
  static class User {

    /**
     * 序列化忽略
     */
    @JSONField(serialize = false)
    private String openId;
    /**
     * 序列化名称为pwd
     */
    @JSONField(name = "pwd")
    private String password;
  }
}

fastjson的JSONField注解提供了多种功能的组合

public class Client2 {

  public static void main(String[] args) throws JsonProcessingException {
    User user = new User();
    user.setUsername("lisi");
    user.setPassword("123456");
    ObjectMapper objectMapper = new ObjectMapper();
    System.out.println(objectMapper.writeValueAsString(user));
  }

  @Setter
  @Getter
  static class User {

    @JsonIgnore
    private String username;
    @JsonProperty("pwd")
    private String password;
  }
}

jackson不同的功能使用不同的注解来实现

json字符串反序列化为java bean

未知属性报错

public class Client1 {

  public static void main(String[] args) {
    String jsonStr = "{\"username\":\"lisi\",\"pwd\":\"123456\"}";
    int featureValue = JSON.DEFAULT_PARSER_FEATURE & ~Feature.IgnoreNotMatch.getMask();
    User user = JSON.parseObject(jsonStr, User.class, featureValue);
    System.out.println(user);
  }

  @Setter
  @Getter
  @ToString
  static class User {

    private String username;
    private String password;
  }
}

fastjson默认会忽略未知属性

所以我们要将忽略未知属性的特性去掉

public class Client2 {

  public static void main(String[] args) throws IOException {
    String jsonStr = "{\"username\":\"lisi\",\"pwd\":\"123456\"}";
    ObjectMapper objectMapper = new ObjectMapper();
    User user = objectMapper.readValue(jsonStr, User.class);
    System.out.println(user);
  }

  @Setter
  @Getter
  @ToString
  static class User {

    private String username;
    private String password;
  }
}

jackson默认未知属性报错

忽略未知属性

public class Client1 {

  public static void main(String[] args) {
    String jsonStr = "{\"username\":\"lisi\",\"pwd\":\"123456\"}";
    User user = JSON.parseObject(jsonStr, User.class);
    System.out.println(user);
  }

  @Setter
  @Getter
  @ToString
  static class User {

    private String username;
    private String password;
  }
}

fastjson默认忽略未知属性

public class Client2 {

  public static void main(String[] args) throws IOException {
    String jsonStr = "{\"username\":\"lisi\",\"pwd\":\"123456\"}";
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    User user = objectMapper.readValue(jsonStr, User.class);
    System.out.println(user);
  }

  @Setter
  @Getter
  @ToString
  static class User {

    private String username;
    private String password;
  }
}

jackson默认未知属性报错，但也提供了反序列化特性来支持忽略。

将java bean 数组序列化为字符串

public class Client1 {

  public static void main(String[] args) {
    List<User> userList = Arrays.asList(new User("lisi", "123"), new User("Tony", "456"));
    System.out.println(JSON.toJSONString(userList));
  }

  @AllArgsConstructor
  @NoArgsConstructor
  @Setter
  @Getter
  @ToString
  static class User {

    private String username;
    private String password;
  }
}

public class Client2 {

  public static void main(String[] args) throws JsonProcessingException {
    List<User> userList = Arrays.asList(new User("lisi", "123"), new User("Tony", "456"));
    ObjectMapper objectMapper = new ObjectMapper();
    System.out.println(objectMapper.writeValueAsString(userList));
  }

  @AllArgsConstructor
  @NoArgsConstructor
  @Setter
  @Getter
  @ToString
  static class User {

    private String username;
    private String password;
  }
}

json字符串反序列化为java bean数组

public class Client1 {

  public static void main(String[] args) {
    String jsonStr = "[{\"username\":\"lisi\",\"password\":\"123\"},{\"username\":\"Tony\",\"password1\":\"456\"}]";
    List<User> userList = JSON.parseArray(jsonStr, User.class);
    System.out.println(userList);
  }

  @Setter
  @Getter
  @ToString
  static class User {

    private String username;
    private String password;
  }
}

fastjson反序列化数组和反序列化bean一样简单

public class Client2 {

  public static void main(String[] args) throws IOException {
    String jsonStr = "[{\"username\":\"lisi\",\"password\":\"123\"},{\"username\":\"Tony\",\"password\":\"456\"}]";
    ObjectMapper objectMapper = new ObjectMapper();
    List<User> userList = objectMapper.readValue(jsonStr, new TypeReference<List<User>>() {
    });
    System.out.println(userList);
  }

  @Setter
  @Getter
  @ToString
  static class User {

    private String username;
    private String password;
  }
}

public class Client2 {

  public static void main(String[] args) throws IOException {
    String jsonStr = "[{\"username\":\"lisi\",\"password\":\"123\"},{\"username\":\"Tony\",\"password\":\"456\"}]";
    ObjectMapper objectMapper = new ObjectMapper();
    //创建一个泛型类型
    JavaType javaType = objectMapper.getTypeFactory()
        .constructParametricType(List.class, User.class);
    List<User> userList = objectMapper.readValue(jsonStr, javaType);
    System.out.println(userList);
  }

  @Setter
  @Getter
  @ToString
  static class User {

    private String username;
    private String password;
  }
}

上述两种方式都可以反序列化泛型集合或集合

fastjson和jackson使用对比

标签：parser   编写   static   figure   ack   结果   png   row   code   

原文地址：https://www.cnblogs.com/strongmore/p/13906831.html