詳解jackson注解（二）jackson反系列化注解

jackson中用于反系列化的主要注解有：

一、JsonCreator

JsonCreator注解在構(gòu)造函數(shù)或者工廠方法上，用于指示實例化類的對象。構(gòu)造函數(shù)或者工廠方法有多個參數(shù)時，參數(shù)必須使用JsonProperty或JacksonInject注解。只有一個參數(shù)時，可以不加。

1、bean

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;

/**
 * @author chushiyan
 * @email  Y2h1c2hpeWFuMDQxNUAxNjMuY29t(base64)
 * @description
 */
public class Linkman implements Serializable {

    public int id;

    public String name;

    public Linkman() {
    }

    @JsonCreator
    // 構(gòu)造函數(shù)或者工廠方法有多個參數(shù)時，參數(shù)必須使用JsonProperty或JacksonInject注解。
    public Linkman(@JsonProperty("linkman_name") String name, @JsonProperty("linkman_id") int id) {
        this.name = name;
        this.id = id;
    }

    @JsonCreator
    // 構(gòu)造函數(shù)或者工廠方法只有一個參數(shù)時，可以不加JsonProperty或JacksonInject注解。
    public Linkman(String name) {
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    
    @Override
    public String toString() {
        return "Linkman{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}

2、測試

（1）測試多個參數(shù)的構(gòu)造函數(shù)：

@Test
    public void testJsonCreate() throws JsonProcessingException {
        String json = "{\"linkman_id\":100,\"linkman_name\":\"chushiyan\"}";
        ObjectMapper mapper = new ObjectMapper();

        Linkman linkman = mapper
                .readerFor(Linkman.class)
                .readValue(json);
        System.out.println(linkman);
    }

控制臺打?。?/p>

Linkman{id=100, name='chushiyan'}

（2）測試只有單個參數(shù)的構(gòu)造函數(shù)

 @Test
    public void testJsonCreate2() throws JsonProcessingException {
        String json = "{\"linkman_name\":\"chushiyan\"}";
        ObjectMapper mapper = new ObjectMapper();

        Linkman linkman = mapper
                .readerFor(Linkman.class)
                .readValue(json);
        System.out.println(linkman);
    }

控制臺打?。?/p>

Linkman{id=0, name='chushiyan'}

二、JsonAlias

@JsonAlias在反序列化時為屬性定義一個或多個別名。

1、bean

import com.fasterxml.jackson.annotation.JsonAlias;
import lombok.Data;

import java.io.Serializable;

/**
 * @author chushiyan
 * @email  Y2h1c2hpeWFuMDQxNUAxNjMuY29t(base64)
 * @description
 */
@Data
public class Customer implements Serializable {

    private String id;
    
    // 為name屬性定義兩個別名
    @JsonAlias({ "customer_name", "CustomerName" })
    private String name;
}

2、測試

    @Test
    public void testJsonAlias() throws JsonProcessingException {
        String json = "{\"id\":100,\"customer_name\":\"chushiyan\"}";
        ObjectMapper mapper = new ObjectMapper();
        Customer customer = mapper
                .readerFor(Customer.class)
                .readValue(json);
        System.out.println(customer);
    }

控制臺打?。?/p>

Customer(id=100, name=chushiyan)

三、JsonSetter

@JsonSetter是@JsonProperty的替代方法。JsonSetter注解在某個方法上，表明這個方法是setter方法

1、bean

import com.fasterxml.jackson.annotation.JsonGetter;
import com.fasterxml.jackson.annotation.JsonSetter;

import java.io.Serializable;

/**
 * @author chushiyan
 * @email Y2h1c2hpeWFuMDQxNUAxNjMuY29t(base64)
 * @description
 */
public class Label implements Serializable {

    private String id;

    private String name;

    @JsonGetter("label_id")
    public String getId() {
        return id;
    }

    @JsonSetter("label_id")
    public void setId(String id) {
        this.id = id;
    }

    @JsonGetter("label_name")
    public String getName() {
        return name;
    }

    @JsonSetter("label_name")
    public void setName(String name) {
        this.name = name;
    }

    public Label() {
    }

    public Label(String id, String name) {
        this.id = id;
        this.name = name;
    }

    @Override
    public String toString() {
        return "Label{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                '}';
    }
}

2、測試

    @Test
    public void testJsonSetter() throws JsonProcessingException {
        Label label = new Label("100", "jackson");
        ObjectMapper mapper = new ObjectMapper();
        String json = mapper.writeValueAsString(label);
        System.out.println(json);
        
        Label label2 = mapper
                .readerFor(Label.class)
                .readValue(json);
        System.out.println(label2);
    }

控制臺打?。?/p>

{"label_id":"100","label_name":"jackson"}
Label{id='100', name='jackson'}

四、JsonAnySetter

反系列化時，@JsonAnySetter注解可以靈活地把類型為Map的屬性作為標準屬性使用。

1、bean

import com.fasterxml.jackson.annotation.JsonAnySetter;
import lombok.Data;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

/**
 * @author chushiyan
 * @email  Y2h1c2hpeWFuMDQxNUAxNjMuY29t(base64)
 * @description
 */
@Data
public class Book implements Serializable {

    private String id;

    @JsonAnySetter
    private Map<String, String> details = new HashMap<String, String>();
}

2、測試

    @Test
    public void testJsonAnySetter() throws JsonProcessingException {
        String json = "{"
                + "\"id\" : \"100\","
                + "\"author\" : \"chushiyan\","
                + "\"price\" : \"30\","
                + "\"category\" : \"IT\""
                + "}";
        ObjectMapper mapper = new ObjectMapper();
        Book book = mapper.readValue(json, Book.class);
        System.out.println(book);
    }

控制臺輸出：

Book(id=100, details={author=chushiyan, price=30, category=IT})