Jackson - 注解 @JsonIgnore 和@JsonIgnoreProperties：忽略字段

将java对象转换为json字符串：

public class JacksonExample1 {
    public static void main(String[] args) {

        ObjectMapper mapper = new ObjectMapper();
        Staff staff = createStaff();

        try {
            // Java objects to JSON string - pretty-print
            String jsonString
                    = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(staff);
            System.out.println(jsonString);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    private static Staff createStaff() {

        Staff staff = new Staff();

        staff.setName("mkyong");
        staff.setAge(38);
        staff.setPosition(new String[]{"Founder", "CTO", "Writer"});
        Map<String, BigDecimal> salary = new HashMap() {{
            put("2010", new BigDecimal(10000));
            put("2012", new BigDecimal(12000));
            put("2018", new BigDecimal(14000));
        }};
        staff.setSalary(salary);
        staff.setSkills(Arrays.asList("java", "python", "node", "kotlin"));

        return staff;
    }
}

默认情况下，Jackson 包括所有字段，甚至是static字段transient。

1. 默认方式

@Data
public class Staff {

    private String name;
    private int age;
    private String[] position;
    private List<String> skills;
    private Map<String, BigDecimal> salary;

}

输出：

{
  "name" : "mkyong",
  "age" : 38,
  "position" : [ "Founder", "CTO", "Writer" ],
  "skills" : [ "java", "python", "node", "kotlin" ],
  "salary" : {
    "2018" : 14000,
    "2012" : 12000,
    "2010" : 10000
  }
}

2. @JsonIgnore 忽略字段级别的字段

@Data
public class Staff {

    private String name;
    private int age;
    private String[] position;

    @JsonIgnore
    private List<String> skills;
    
    @JsonIgnore
    private Map<String, BigDecimal> salary;
}

输出：

{
  "name" : "mkyong",
  "age" : 38,
  "position" : [ "Founder", "CTO", "Writer" ]
}

3. @JsonIgnoreProperties 忽略类级别的字段

@JsonIgnoreProperties({"salary", "position"})
@Data
public class Staff {

    private String name;
    private int age;
    private String[] position;
    private List<String> skills;
    private Map<String, BigDecimal> salary;
    
}

输出：

{
  "name" : "mkyong",
  "age" : 38,
  "skills" : [ "java", "python", "node", "kotlin" ]
}