Json解析工具Jackson（使用註解）

http://blog.csdn.net/nomousewch/article/details/8955796

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        接上一篇文章Json解析工具Jackson（簡單應用），jackson在實際應用中給咱們提供了一系列註解，提升了開發的靈活性，下面介紹一下最經常使用的一些註解

• @JsonIgnoreProperties

         此註解是類註解，做用是json序列化時將Java bean中的一些屬性忽略掉，序列化和反序列化都受影響。

• @JsonIgnore

         此註解用於屬性或者方法上（最好是屬性上），做用和上面的@JsonIgnoreProperties同樣。

• @JsonFormat

        此註解用於屬性或者方法上（最好是屬性上），能夠方便的把Date類型直接轉化爲咱們想要的模式，好比@JsonFormat(pattern = "yyyy-MM-dd HH-mm-ss")

• @JsonSerialize

        此註解用於屬性或者getter方法上，用於在序列化時嵌入咱們自定義的代碼，好比序列化一個double時在其後面限制兩位小數點。

public class CustomDoubleSerialize extends JsonSerializer<Double> {

    private DecimalFormat df = new DecimalFormat("##.00");

    @Override
    public void serialize(Double value, JsonGenerator jgen,
            SerializerProvider provider) throws IOException,
            JsonProcessingException {

        jgen.writeString(df.format(value));
    }
}

• @JsonDeserialize

         此註解用於屬性或者setter方法上，用於在反序列化時能夠嵌入咱們自定義的代碼，相似於上面的@JsonSerialize

public class CustomDateDeserialize extends JsonDeserializer<Date> {

    private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

    @Override
    public Date deserialize(JsonParser jp, DeserializationContext ctxt)
            throws IOException, JsonProcessingException {

        Date date = null;
        try {
            date = sdf.parse(jp.getText());
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return date;
    }
}

• 完整例子

       

//表示序列化時忽略的屬性
@JsonIgnoreProperties(value = { "word" })
public class Person {
    private String name;
    private int age;
    private boolean sex;
    private Date birthday;
    private String word;
    private double salary;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public boolean isSex() {
        return sex;
    }

    public void setSex(boolean sex) {
        this.sex = sex;
    }

    public Date getBirthday() {
        return birthday;
    }

    // 反序列化一個固定格式的Date
    @JsonDeserialize(using = CustomDateDeserialize.class)
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getWord() {
        return word;
    }

    public void setWord(String word) {
        this.word = word;
    }

    // 序列化指定格式的double格式
    @JsonSerialize(using = CustomDoubleSerialize.class)
    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public Person(String name, int age, boolean sex, Date birthday,
            String word, double salary) {
        super();
        this.name = name;
        this.age = age;
        this.sex = sex;
        this.birthday = birthday;
        this.word = word;
        this.salary = salary;
    }

    public Person() {
    }

    @Override
    public String toString() {
        return "Person [name=" + name + ", age=" + age + ", sex=" + sex
                + ", birthday=" + birthday + ", word=" + word + ", salary="
                + salary + "]";
    }

}

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

        writeJsonObject();

        // readJsonObject();
    }

    // 直接寫入一個對象(所謂序列化)
    public static void writeJsonObject() {
        ObjectMapper mapper = new ObjectMapper();
        Person person = new Person("nomouse", 25, true, new Date(), "程序員",
                2500.0);
        try {
            mapper.writeValue(new File("c:/person.json"), person);
        } catch (JsonGenerationException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 直接將一個json轉化爲對象（所謂反序列化）
    public static void readJsonObject() {
        ObjectMapper mapper = new ObjectMapper();

        try {
            Person person = mapper.readValue(new File("c:/person.json"),
                    Person.class);
            System.out.println(person.toString());
        } catch (JsonParseException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


}