Json解析工具Jackson（使用注解）
接上一篇文章Json解析工具Jackson（简单应用），jackson在实际应用中给我们提供了一系列注解，提高了开发的灵活性，下面介绍一下最常用的一些注解
- @JsonIgnoreProperties
此注解是类注解，作用是json序列化时将java bean中的一些属性忽略掉，序列化和反序列化都受影响。
- @JsonIgnore
此注解用于属性或者方法上（最好是属性上），作用和上面的@JsonIgnoreProperties一样。
- @JsonFormat
此注解用于属性或者方法上（最好是属性上），可以方便的把Date类型直接转化为我们想要的模式，比如@JsonFormat(pattern= "yyyy-MM-dd HH-mm-ss")
- @JsonSerialize
此注解用于属性或者getter方法上，用于在序列化时嵌入我们自定义的代码，比如序列化一个double时在其后面限制两位小数点。
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1. public class CustomDoubleSerialize extends JsonSerializer
2.
3. private DecimalFormat df = new DecimalFormat("##.00");
4.
5. @Override
6. public void serialize(Double value, JsonGenerator jgen,
7. SerializerProvider provider) throws IOException,
8. JsonProcessingException {
9.
10. jgen.writeString(df.format(value));
11. }
12.}
- @JsonDeserialize
此注解用于属性或者setter方法上，用于在反序列化时可以嵌入我们自定义的代码，类似于上面的@JsonSerialize
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1. public class CustomDateDeserialize extends JsonDeserializer
2.
3. private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
4.
5. @Override
6. public Date deserialize(JsonParser jp, DeserializationContext ctxt)
7. throws IOException, JsonProcessingException {
8.
9. Date date = null;
10. try {
11. date = sdf.parse(jp.getText());
12. } catch (ParseException e) {
13. e.printStackTrace();
14. }
15. return date;
16. }
17. }
- 完整例子
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1. //表示序列化时忽略的属性
2. @JsonIgnoreProperties(value = { "word" })
3. public class Person {
4. private String name;
5. private int age;
6. private boolean sex;
7. private Date birthday;
8. private String word;
9. private double salary;
10.
11. public String getName() {
12. return name;
13. }
14.
15. public void setName(String name) {
16. this.name = name;
17. }
18.
19. public int getAge() {
20. return age;
21. }
22.
23. public void setAge(int age) {
24. this.age = age;
25. }
26.
27. public boolean isSex() {
28. return sex;
29. }
30.
31. public void setSex(boolean sex) {
32. this.sex = sex;
33. }
34.
35. public Date getBirthday() {
36. return birthday;
37. }
38.
39. // 反序列化一个固定格式的Date
40. @JsonDeserialize(using = CustomDateDeserialize.class)
41. public void setBirthday(Date birthday) {
42. this.birthday = birthday;
43. }
44.
45. public String getWord() {
46. return word;
47. }
48.
49. public void setWord(String word) {
50. this.word = word;
51. }
52.
53. // 序列化指定格式的double格式
54. @JsonSerialize(using = CustomDoubleSerialize.class)
55. public double getSalary() {
56. return salary;
57. }
58.
59. public void setSalary(double salary) {
60. this.salary = salary;
61. }
62.
63. public Person(String name, int age) {
64. this.name = name;
65. this.age = age;
66. }
67.
68. public Person(String name, int age, boolean sex, Date birthday,
69. String word, double salary) {
70. super();
71. this.name = name;
72. this.age = age;
73. this.sex = sex;
74. this.birthday = birthday;
75. this.word = word;
76. this.salary = salary;
77. }
78.
79. public Person() {
80. }
81.
82. @Override
83. public String toString() {
84. return "Person [name=" + name + ", age=" + age + ", sex=" + sex
85. + ", birthday=" + birthday + ", word=" + word + ", salary="
86. + salary + "]";
87. }
88.
89. }
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1. public class Demo {
2. public static void main(String[] args) {
3.
4. writeJsonObject();
5.
6. // readJsonObject();
7. }
8.
9. // 直接写入一个对象(所谓序列化)
10. public static void writeJsonObject() {
11. ObjectMapper mapper = new ObjectMapper();
12. Person person = new Person("nomouse", 25, true, new Date(), "程序员",
13. 2500.0);
14. try {
15. mapper.writeValue(new File("c:/person.json"), person);
16. } catch (JsonGenerationException e) {
17. e.printStackTrace();
18. } catch (JsonMappingException e) {
19. e.printStackTrace();
20. } catch (IOException e) {
21. e.printStackTrace();
22. }
23. }
24.
25. // 直接将一个json转化为对象（所谓反序列化）
26. public static void readJsonObject() {
27. ObjectMapper mapper = new ObjectMapper();
28.
29. try {
30. Person person = mapper.readValue(new File("c:/person.json"),
31. Person.class);
32. System.out.println(person.toString());
33. } catch (JsonParseException e) {
34. e.printStackTrace();
35. } catch (JsonMappingException e) {
36. e.printStackTrace();
37. } catch (IOException e) {
38. e.printStackTrace();
39. }
40. }
41.
42.
43. }