fastjson 指定系列化格式

public static void main(String[] args) {
        List<User> list = new ArrayList<>();
        list.add(new User(1,"11","11"));
        list.add(new User(2,"22","22"));
        list.add(new User(3,"33","33"));
        String buildData = buildData(list);
        System.out.println(buildData);
        // [{"id":1,"user_age":"11","user_name":"11"},{"id":2,"user_age":"22","user_name":"22"},{"id":3,"user_age":"33","user_name":"33"}]
        String buildData2 = buildData2(list);
        System.out.println(buildData2);
        // [{"id":1,"userAge":"11","userName":"11"},{"id":2,"userAge":"22","userName":"22"},{"id":3,"userAge":"33","userName":"33"}]
        String buildData3 = buildData3(list);
        System.out.println(buildData3);
        // [{"id":1,"user-age":"11","user-name":"11"},{"id":2,"user-age":"22","user-name":"22"},{"id":3,"user-age":"33","user-name":"33"}]
    }

    public static String buildData(Object bean) {
        try {
            SerializeConfig CONFIG = new SerializeConfig();
            CONFIG.propertyNamingStrategy = PropertyNamingStrategy.SnakeCase;
            return JSON.toJSONString(bean, CONFIG);
        } catch (Exception e) {
            return null;
        }
    }

    public static String buildData2(Object bean) {
        try {
            SerializeConfig CONFIG = new SerializeConfig();
            CONFIG.propertyNamingStrategy = PropertyNamingStrategy.CamelCase;
            return JSON.toJSONString(bean, CONFIG);
        } catch (Exception e) {
            return null;
        }
    }

    public static String buildData3(Object bean) {
        try {
            SerializeConfig CONFIG = new SerializeConfig();
            CONFIG.propertyNamingStrategy = PropertyNamingStrategy.KebabCase;
            return JSON.toJSONString(bean, CONFIG);
        } catch (Exception e) {
            return null;
        }
    }

最好先实例化，否则运行过程会频繁创建，详情参考别人的（https://www.cnblogs.com/rude3knife/p/13570423.html）

private static final SerializeConfig CONFIG = new SerializeConfig();

    static {
        CONFIG.propertyNamingStrategy = PropertyNamingStrategy.SnakeCase;
    }

PropertyNamingStrategy 枚举类

package com.alibaba.fastjson;

/**
 * @since 1.2.15
 */
public enum PropertyNamingStrategy {
                                    CamelCase, //
                                    PascalCase, //
                                    SnakeCase, //
                                    KebabCase;

    public String translate(String propertyName) {
        switch (this) {
            case SnakeCase: {
                StringBuilder buf = new StringBuilder();
                for (int i = 0; i < propertyName.length(); ++i) {
                    char ch = propertyName.charAt(i);
                    if (ch >= 'A' && ch <= 'Z') {
                        char ch_ucase = (char) (ch + 32);
                        if (i > 0) {
                            buf.append('_');
                        }
                        buf.append(ch_ucase);
                    } else {
                        buf.append(ch);
                    }
                }
                return buf.toString();
            }
            case KebabCase: {
                StringBuilder buf = new StringBuilder();
                for (int i = 0; i < propertyName.length(); ++i) {
                    char ch = propertyName.charAt(i);
                    if (ch >= 'A' && ch <= 'Z') {
                        char ch_ucase = (char) (ch + 32);
                        if (i > 0) {
                            buf.append('-');
                        }
                        buf.append(ch_ucase);
                    } else {
                        buf.append(ch);
                    }
                }
                return buf.toString();
            }
            case PascalCase: {
                char ch = propertyName.charAt(0);
                if (ch >= 'a' && ch <= 'z') {
                    char[] chars = propertyName.toCharArray();
                    chars[0] -= 32;
                    return new String(chars);
                }

                return propertyName;
            }
            case CamelCase: {
                char ch = propertyName.charAt(0);
                if (ch >= 'A' && ch <= 'Z') {
                    char[] chars = propertyName.toCharArray();
                    chars[0] += 32;
                    return new String(chars);
                }

                return propertyName;
            }
            default:
                return propertyName;
        }
    }
}

fastjson SerializeConfig 做了什么

SerializeConfig介绍：

SerializeConfig的主要功能是配置并记录每种Java类型对应的序列化类（ObjectSerializer接口的实现类），
比如Boolean.class使用BooleanCodec（看命名就知道该类将序列化和反序列化实现写到一起了）作为序列化实现类，
float[].class使用FloatArraySerializer作为序列化实现类。这些序列化实现类，有的是FastJSON中默认实现的（比如Java基本类），
有的是通过ASM框架生成的（比如用户自定义类），有的甚至是用户自定义的序列化类（比如Date类型框架默认实现是转为毫秒，应用需要转为秒）。
当然，这就涉及到是使用ASM生成序列化类还是使用JavaBean的序列化类类序列化的问题，这里判断根据就是是否Android环境（环境变量"java.vm.name"为"dalvik"
或"lemur"就是Android环境），但判断不仅这里一处，后续还有更具体的判断。

理论上来说，每个SerializeConfig实例若序列化相同的类，都会找到之前生成的该类的代理类，来进行序列化。们的服务在每次接口被调用时，都实例化一个ParseConfig对象来配置Fastjson反序列的设置，而未禁用ASM代理的情况下，由于每次调用ParseConfig都是一个新的实例，因此永远也检查不到已经创建的代理类，所以Fastjson便不断的创建新的代理类，并加载到metaspace中，最终导致metaspace不断扩张，将机器的内存耗尽。

原文： https://www.cnblogs.com/rude3knife/p/13570423.html