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关于json:Fastjson处理枚举

Fastjson

这玩意儿不多说,Alibaba 出品,出过几次重大的安全漏洞,然而仍然很风行。这里写一下它怎么解决枚举。

<!-- https://mvnrepository.com/artifact/com.alibaba/fastjson -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.76</version>
</dependency>

序列化为 name()值

默认就是,啥也不必动

import com.alibaba.fastjson.JSON;

enum Gender {BOY, GIRL, UNKNOW}

class User {
    private Integer id;
    private Gender gender;
    public User() {}
    public User(Integer id, Gender gender) {super();
        this.id = id;
        this.gender = gender;
    }

    public Integer getId() {return id;}

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

    public Gender getGender() {return gender;}

    public void setGender(Gender gender) {this.gender = gender;}
}

public class MainTest {public static void main(String[] args) throws Exception {
        
        // 序列化为 JSON 输入
        User user = new User(1, Gender.BOY);
        String jsonString = JSON.toJSONString(user); 
        System.out.println(jsonString);    // {"gender":"BOY","id":1}
        
        
        // 反序列化为对象
        user = JSON.parseObject(jsonString, User.class);
        System.out.println(user.getGender());        // BOY
    }
}

序列化为 ordinal()值

全局设置

代码跟下面没有变动,就须要在结尾增加一句代码,任何枚举,都会被序列化为 ordinal()值

JSON.DEFAULT_GENERATE_FEATURE &= ~SerializerFeature.WriteEnumUsingName.mask;
        // 全局设置,枚举的序列化应用 ordinal()
        JSON.DEFAULT_GENERATE_FEATURE &= ~SerializerFeature.WriteEnumUsingName.mask;
        
        // 序列化为 JSON 输入,枚举值为 ordinal()
        User user = new User(1, Gender.BOY);
        String jsonString = JSON.toJSONString(user); 
        System.out.println(jsonString);    // {"gender":0,"id":1}
        
        
        // 反序列化为对象
        user = JSON.parseObject(jsonString, User.class);
        System.out.println(user.getGender());        // BOY

非凡设置

只想针对某一次序列化失效。只须要调用 JSON.toJSONString 的重载办法,增加配置就行。

public static String toJSONString(Object object, int defaultFeatures, SerializerFeature... features)
        // 序列化为 JSON 输入,本次把枚举值序列化为 ordinal()
        User user = new User(1, Gender.BOY);
        String jsonString = JSON.toJSONString(user, JSON.DEFAULT_GENERATE_FEATURE & ~SerializerFeature.WriteEnumUsingName.mask); 
        System.out.println(jsonString);    // {"gender":0,"id":1}
        
        
        // 反序列化为对象
        user = JSON.parseObject(jsonString, User.class);
        System.out.println(user.getGender());        // BOY

序列化为自定义属性

很多人也喜爱给枚举定义一个公有的属性,序列化为 JSON 时,心愿以这个属性值作为 value,这个时候就须要本人定义 JSON 的序列化和反序列化实现了。Fastjson 提供了 2 个接口。用户管制序列化和反序列化行为,这个切实是太简略,这里不多说。看代码

  • ObjectSerializer
  • ObjectDeserializer

序列化器的定义

import java.io.IOException;
import java.lang.reflect.Type;

import com.alibaba.fastjson.serializer.JSONSerializer;
import com.alibaba.fastjson.serializer.ObjectSerializer;

public class GenderEnumSerializer implements ObjectSerializer {
    @Override
    public void write(JSONSerializer serializer, Object object, Object fieldName, Type fieldType, int features) throws IOException {
        // 强制把值转换为 Gender
        Gender gender = (Gender) object;
        // 序列化为自定义的 name 属性,输入就行
        serializer.out.writeString(gender.getName());
    }
}

反序列化器的定义

import java.lang.reflect.Type;

import com.alibaba.fastjson.parser.DefaultJSONParser;
import com.alibaba.fastjson.parser.JSONToken;
import com.alibaba.fastjson.parser.deserializer.ObjectDeserializer;

public class GenderEnumDeserializer implements ObjectDeserializer {@SuppressWarnings("unchecked")
    @Override
    public <T> T deserialze(DefaultJSONParser parser, Type type, Object fieldName) {
        // 解析值为字符串
        String value = parser.parseObject(String.class);
        // 遍历所有的枚举实例
        for (Gender gender : Gender.values()) {if (gender.getName().equals(value)) {
                // 胜利匹配,返回实例
                return (T) gender;
            }
        }
        // 没有匹配到,能够抛出异样或者返回 null
        return null;
    }

    @Override
    public int getFastMatchToken() {
        // 仅仅匹配字符串类型的值
        return JSONToken.LITERAL_STRING;
    }
}

对象 & 枚举的定义

enum Gender {BOY("男"), GIRL("女"), UNKNOW("不晓得");
    
    public final String name;
    
    Gender(String name) {this.name = name;}
    public String getName() {return name;}
}


class User {
    
    private Integer id;
    
    // 标识注解,指定枚举的序列化。反序列化实现类
    @JSONField(serializeUsing = GenderEnumSerializer.class, deserializeUsing = GenderEnumDeserializer.class)
    private Gender gender;

    public User() {}

    public User(Integer id, Gender gender) {super();
        this.id = id;
        this.gender = gender;
    }

    public Integer getId() {return id;}

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

    public Gender getGender() {return gender;}

    public void setGender(Gender gender) {this.gender = gender;}
}

测试

public class MainTest {public static void main(String[] args) throws Exception {// 序列化为 JSON 输入,枚举值为 getName()
        User user = new User(1, Gender.UNKNOW);
        String jsonString = JSON.toJSONString(user);
        System.out.println(jsonString); // {"gender":"不晓得","id":1}

        // 反序列化为对象
        user = JSON.parseObject(jsonString, User.class);
        System.out.println(user.getGender()); // UNKNOW
    }
}

最初

很显然,自定义 ObjectSerializer /ObjectDeserializer 的形式最为灵便,能够思考形象一个接口进去,让所有的枚举都实现接口。这样针对接口编写 ObjectSerializer /ObjectDeserializer 实现,就能够很好的复用了。


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