使用Fastjson进行JSON生成与解析的新手指南

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>2.0.39</version> <!-- 使用最新安全版本 -->
</dependency>

import com.alibaba.fastjson.JSON;

User user = new User("张三", 25);
String json = JSON.toJSONString(user);
// 输出：{"name":"张三","age":25}

String json = "{\"name\":\"李四\",\"age\":30}";
User user = JSON.parseObject(json, User.class);

public class User {
    @JSONField(name = "user_name")  // 自定义字段名
    private String name;

    @JSONField(serialize = false)   // 忽略字段
    private String password;

    @JSONField(format = "yyyy-MM-dd HH:mm:ss")  // 日期格式化
    private Date createTime;
}

@JSONType(orders = {"id", "name", "age"}) // 指定字段顺序
public class User {
    private Long id;
    private String name;
    private Integer age;
}

// 序列化配置
SerializeConfig config = new SerializeConfig();
config.put(Date.class, new SimpleDateFormatSerializer("yyyy-MM-dd"));

// 反序列化配置
ParserConfig parserConfig = new ParserConfig();
parserConfig.setSafeMode(true); // 启用安全模式防漏洞

String json = JSON.toJSONString(obj, config);
User user = JSON.parseObject(json, User.class, parserConfig);

public class MoneySerializer implements ObjectSerializer {
    @Override
    public void write(
        JSONSerializer serializer, 
        Object value, 
        Object fieldName, 
        Type fieldType, 
        int features
    ) {
        BigDecimal amount = (BigDecimal) value;
        serializer.write(amount.setScale(2) + "元");
    }
}

​​​​​​​// 注册自定义序列化器
SerializeConfig.getGlobalInstance().put(BigDecimal.class, new MoneySerializer());

// 序列化
List<User> users = Arrays.asList(new User("张三"), new User("李四"));
String json = JSON.toJSONString(users);

// 反序列化
List<User> parsedUsers = JSON.parseArray(json, User.class);

// 禁用循环检测（默认开启，可能导致StackOverflow）
String json = JSON.toJSONString(obj, SerializerFeature.DisableCircularReferenceDetect);

User user = JSON.parseObject(json, User.class, Feature.IgnoreNotMatch);

// 提升序列化速度（牺牲严格校验）
String json = JSON.toJSONString(obj, 
    SerializerFeature.WriteMapNullValue, 
    SerializerFeature.DisableCheckSpecialChar
);

try (JSONWriter writer = new JSONWriter(new FileWriter("large.json"))) {
    writer.startArray();
    for (User user : users) {
        writer.writeValue(user);
    }
    writer.endArray();
}

ParserConfig.getGlobalInstance().setSafeMode(true); // 禁止反序列化任意类

// 只允许反序列化指定类
ParserConfig.getGlobalInstance().addAccept("com.example.model.");

@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
        converter.setFastJsonConfig(fastJsonConfig());
        converters.add(0, converter);
    }

    private FastJsonConfig fastJsonConfig() {
        FastJsonConfig config = new FastJsonConfig();
        config.setSerializerFeatures(SerializerFeature.PrettyFormat);
        config.setDateFormat("yyyy-MM-dd HH:mm:ss");
        return config;
    }
}

// 全局配置日期格式
JSON.DEFFAULT_DATE_FORMAT = "yyyy-MM-dd";
String json = JSON.toJSONString(new Date()); // 输出 "2023-01-01"

// 驼峰转下划线命名
Model model = new Model();
model.setUserName("test");
String json = JSON.toJSONString(model, SerializerFeature.UseSnakeCase);
// 输出 {"user_name":"test"}

public enum Status {
    @JSONField(name = "OK")  // 自定义枚举值名称
    SUCCESS,
    @JSONField(name = "ERR")
    FAILED
}

String json = JSON.toJSONString(Status.SUCCESS); // 输出 "OK"