<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.15.0</version>
</dependency>

// 序列化Java對象→JSON
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(user); 
// 反序列化JSON→Java對象
User user = mapper.readValue(json, User.class);

// 處理日期格式
mapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
// 忽略未知屬性
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
// 美化輸出
String prettyJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(user);

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.10.1</version>
</dependency>

@Bean
public HttpMessageConverters gsonConverter() {
    Gson gson = new GsonBuilder()
            .setDateFormat("yyyy-MM-dd")
            .create();
    return new HttpMessageConverters(new GsonHttpMessageConverter(gson));
}

Gson gson = new Gson();
// 對象→JSON
String json = gson.toJson(user);
// JSON→對象
User user = gson.fromJson(json, User.class);
// 處理泛型集合
Type listType = new TypeToken<List<User>>(){}.getType();
List<User> users = gson.fromJson(jsonArray, listType);

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>2.0.34</version>
</dependency>

@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,
            SerializerFeature.WriteMapNullValue
        );
        config.setDateFormat("yyyy-MM-dd HH:mm:ss");
        return config;
    }
}

// 序列化
String json = JSON.toJSONString(user, SerializerFeature.WriteDateUseDateFormat);
// 反序列化
User user = JSON.parseObject(json, User.class);
// 解析JSON數(shù)組
List<User> users = JSON.parseArray(jsonArray, User.class);

public class MoneySerializer extends JsonSerializer<BigDecimal> {
    @Override
    public void serialize(BigDecimal value, 
                          JsonGenerator gen, 
                          SerializerProvider provider) {
        gen.writeString(value.setScale(2, RoundingMode.HALF_UP) + "元");
    }
}
// 在實體類中使用
public class Order {
    @JsonSerialize(using = MoneySerializer.class)
    private BigDecimal amount;
}

@JsonTypeInfo(use = Id.NAME, include = As.PROPERTY, property = "type")
@JsonSubTypes({
    @Type(value = Dog.class, name = "dog"),
    @Type(value = Cat.class, name = "cat")
})
public abstract class Animal {}
// 序列化時將自動添加"type":"dog"字段

try(JsonParser parser = mapper.createParser(new File("large.json"))) {
    while (parser.nextToken() != null) {
        JsonToken token = parser.currentToken();
        if (token == JsonToken.FIELD_NAME && "name".equals(parser.getText())) {
            parser.nextToken();
            System.out.println(parser.getText());
        }
    }
}

# application.yml
spring:
  jackson:
    date-format: yyyy-MM-dd HH:mm:ss
    time-zone: GMT+8

// 使用Jackson的壓縮特性
mapper.configure(JsonGenerator.Feature.WRITE_BIGDECIMAL_AS_PLAIN, true);

// 反序列化時設(shè)置最大長度
factory.setStreamReadConstraints(StreamReadConstraints.builder()
    .maxStringLength(10_000_000).build());

@JsonFormat(pattern = "yyyy/MM/dd", timezone = "Asia/Shanghai")
private Date birthDate;

@JsonInclude(Include.NON_NULL)  // Jackson
@Expose(serialize = false)      // Gson
private String optionalField;

@JsonProperty("user_name")      // Jackson
@SerializedName("user_name")    // Gson
private String username;