关于java:常见Bean拷贝框架下划线驼峰互转扩展支持

上一篇博文常见Bean拷贝框架应用姿态及性能比照介绍了几种bean拷贝框架的应用姿态以及性能比照，次要实用的是属性名统一、类型统一的拷贝，在理论的业务开发中，常常会用到驼峰和下划线的互转，本文在之前的根底上进行扩大

cglib
hutool

常见Bean拷贝框架下划线驼峰互转扩大反对

I. 驼峰下划线拷贝反对

下面的应用都是最根本的应用姿态，属性名 + 类型统一，都有getter/setter办法，咱们理论的业务场景中，有一个比拟重要的中央，就是下划线与驼峰的转换反对，如果要应用下面的框架，能够怎么适配?

1. cglib 下划线转驼峰

spring cglib封装与污浊版的cglib 实现逻辑差异不大，次要是spring外面做了一些缓存，所以体现会绝对好一点；为了更加通用，这里以污浊版的cglib进行扩大演示

cglib实现转换的外围逻辑在 net.sf.cglib.beans.BeanCopier.Generator.generateClass

public void generateClass(ClassVisitor v) {    // ... 省略无关代码    PropertyDescriptor[] getters = ReflectUtils.getBeanGetters(source);    PropertyDescriptor[] setters = ReflectUtils.getBeanSetters(target);        // 扫描source的所有getter办法，写入到map， key为属性名;     // 为了反对驼峰，下划线，咱们能够扩大一下这个map，如果属性名为下划线的，额定加一个驼峰的kv进去     Map names = new HashMap();    for (int i = 0; i < getters.length; i++) {        names.put(getters[i].getName(), getters[i]);    }       // ...    for (int i = 0; i < setters.length; i++) {        PropertyDescriptor setter = setters[i];        // 这里依据target的属性名，获取source对应的getter办法，同样适配一下，如果下划线格局的获取不到，则改用驼峰的试一下        PropertyDescriptor getter = (PropertyDescriptor)names.get(setter.getName());        if (getter != null) {           // ....        }    }   // ...}

革新逻辑，下面的正文中曾经贴出来了，外围实现就比较简单了

提供一个下划线转驼峰的工具了 StrUtil

public class StrUtil {    private static final char UNDER_LINE = '_';    /**     * 下划线转驼峰     *     * @param name     * @return     */    public static String toCamelCase(String name) {        if (null == name || name.length() == 0) {            return null;        }        if (!contains(name, UNDER_LINE)) {            return name;        }        int length = name.length();        StringBuilder sb = new StringBuilder(length);        boolean underLineNextChar = false;        for (int i = 0; i < length; ++i) {            char c = name.charAt(i);            if (c == UNDER_LINE) {                underLineNextChar = true;            } else if (underLineNextChar) {                sb.append(Character.toUpperCase(c));                underLineNextChar = false;            } else {                sb.append(c);            }        }        return sb.toString();    }    public static boolean contains(String str, char searchChar) {        return str.indexOf(searchChar) >= 0;    }}

而后自定义一个 PureCglibBeanCopier, 将之前BeanCopier的代码都拷贝进来，而后改一下下面正文的两个中央 (残缺的代码参考我的项目源码)

public void generateClass(ClassVisitor v) {    // ... 省略无关代码    PropertyDescriptor[] setters = ReflectUtils.getBeanSetters(target);        // 扫描source的所有getter办法，写入到map， key为属性名;     // 为了反对驼峰，下划线，咱们能够扩大一下这个map，如果属性名为下划线的，额定加一个驼峰的kv进去     Map<String, PropertyDescriptor> names = buildGetterNameMapper(source)       // ...    for (int i = 0; i < setters.length; i++) {        PropertyDescriptor setter = setters[i];        // 这里依据target的属性名，获取source对应的getter办法，同样适配一下，如果下划线格局的获取不到，则改用驼峰的试一下        PropertyDescriptor getter = loadSourceGetter(names, setter);        if (getter != null) {           // ....        }    }   // ...}/** * 获取指标的getter办法，反对下划线与驼峰 * * @param source * @return */public Map<String, PropertyDescriptor> buildGetterNameMapper(Class source) {    PropertyDescriptor[] getters = org.springframework.cglib.core.ReflectUtils.getBeanGetters(source);    Map<String, PropertyDescriptor> names = new HashMap<>(getters.length);    for (int i = 0; i < getters.length; ++i) {        String name = getters[i].getName();        String camelName = StrUtil.toCamelCase(name);        names.put(name, getters[i]);        if (!name.equalsIgnoreCase(camelName)) {            // 反对下划线转驼峰            names.put(camelName, getters[i]);        }    }    return names;}/** * 依据target的setter办法，找到source的getter办法，反对下划线与驼峰的转换 * * @param names * @param setter * @return */public PropertyDescriptor loadSourceGetter(Map<String, PropertyDescriptor> names, PropertyDescriptor setter) {    String setterName = setter.getName();    return names.getOrDefault(setterName, names.get(StrUtil.toCamelCase(setterName)));}

应用姿态和之前没有什么区别，就是BeanCopier的创立这里稍稍批改一下即可（BeanCopier能够加缓存，防止频繁的创立）

public <K, T> T copyAndParse(K source, Class<T> target) throws IllegalAccessException, InstantiationException {    // todo copier 能够缓存起来，防止每次从新创立    BeanCopier copier = PureCglibBeanCopier.create(source.getClass(), target, false);    T res = target.newInstance();    copier.copy(source, res, null);    return res;}

2. hutool 下划线转驼峰

hutool也反对下划线与驼峰的互转，而且不须要批改源码，只用咱们本人保护一个FieldMapper即可，改变老本较小；而且在map2bean, bean2map时，能够无批改的实现驼峰下划线互转，这一点还是十分很优良的

/** * 驼峰转换 * * @param source * @param target * @param <K> * @param <T> * @return */public <K, T> T copyAndParse(K source, Class<T> target) throws Exception {    T res = target.newInstance();    // 下划线转驼峰    BeanUtil.copyProperties(source, res, getCopyOptions(source.getClass()));    return res;}// 缓存CopyOptions（留神这个是HuTool的类，不是Cglib的）private Map<Class, CopyOptions> cacheMap = new HashMap<>();private CopyOptions getCopyOptions(Class source) {    CopyOptions options = cacheMap.get(source);    if (options == null) {        // 不加锁，咱们认为反复执行不会比并发加锁带来的开销大        options = CopyOptions.create().setFieldMapping(buildFieldMapper(source));        cacheMap.put(source, options);    }    return options;}/** * @param source * @return */private Map<String, String> buildFieldMapper(Class source) {    PropertyDescriptor[] properties = ReflectUtils.getBeanProperties(source);    Map<String, String> map = new HashMap<>();    for (PropertyDescriptor target : properties) {        String name = target.getName();        String camel = StrUtil.toCamelCase(name);        if (!name.equalsIgnoreCase(camel)) {            map.put(name, camel);        }        String under = StrUtil.toUnderlineCase(name);        if (!name.equalsIgnoreCase(under)) {            map.put(name, under);        }    }    return map;}

3. mapstruct

最初再介绍一下MapStruct，尽管咱们须要手动编码来实现转换，然而益处是性能高啊，既然曾经手动编码了，那也就不介意补上下划线和驼峰的转换了

@Mappings({        @Mapping(target = "userName", source = "user_name"),        @Mapping(target = "market_price", source = "marketPrice")})Target2 copyAndParse(Source source);

4. 测试

接下来测试一下下面三个是否能失常工作

定义一个Target2，留神它与Source有两个字段不同，别离是 user_name/userName, marketPrice/market_price

@Datapublic class Target2 {    private Integer id;    private String userName;    private Double price;    private List<Long> ids;    private BigDecimal market_price;}private void camelParse() throws Exception {    Source s = genSource();    Target2 cglib = springCglibCopier.copyAndParse(s, Target2.class);    Target2 cglib2 = pureCglibCopier.copyAndParse(s, Target2.class);    Target2 hutool = hutoolCopier.copyAndParse(s, Target2.class);    Target2 map = mapsCopier.copy(s, Target2.class);    System.out.println("source:" + s + "\nsCglib:" + cglib + "\npCglib:" + cglib2 + "\nhuTool:" + hutool + "\nMapStruct:" + map);}

输入后果如下

source:Source(id=527180337, user_name=一灰灰Blog, price=7.9, ids=[-2509965589596742300, 5995028777901062972, -1914496225005416077], marketPrice=0.35188996791839599609375)sCglib:Target2(id=527180337, userName=一灰灰Blog, price=7.9, ids=[-2509965589596742300, 5995028777901062972, -1914496225005416077], market_price=0.35188996791839599609375)pCglib:Target2(id=527180337, userName=一灰灰Blog, price=7.9, ids=[-2509965589596742300, 5995028777901062972, -1914496225005416077], market_price=0.35188996791839599609375)huTool:Target2(id=527180337, userName=一灰灰Blog, price=7.9, ids=[-2509965589596742300, 5995028777901062972, -1914496225005416077], market_price=0.35188996791839599609375)MapStruct:Target2(id=527180337, userName=一灰灰Blog, price=7.9, ids=[-2509965589596742300, 5995028777901062972, -1914496225005416077], market_price=0.35188996791839599609375)

性能测试

private <T> void autoCheck2(Class<T> target, int size) throws Exception {    StopWatch stopWatch = new StopWatch();    runCopier(stopWatch, "apacheCopier", size, (s) -> apacheCopier.copy(s, target));    runCopier(stopWatch, "springCglibCopier", size, (s) -> springCglibCopier.copyAndParse(s, target));    runCopier(stopWatch, "pureCglibCopier", size, (s) -> pureCglibCopier.copyAndParse(s, target));    runCopier(stopWatch, "hutoolCopier", size, (s) -> hutoolCopier.copyAndParse(s, target));    runCopier(stopWatch, "springBeanCopier", size, (s) -> springBeanCopier.copy(s, target));    runCopier(stopWatch, "mapStruct", size, (s) -> mapsCopier.copyAndParse(s,  target));    System.out.println((size / 10000) + "w -------- cost: " + stopWatch.prettyPrint());}

比照后果如下，尽管cglib, hutool 反对了驼峰,下划线的互转，最终的体现和下面的也没什么太大区别

1w -------- cost: StopWatch '': running time = 754589100 ns---------------------------------------------ns         %     Task name---------------------------------------------572878100  076%  apacheCopier yihui017037900  002%  springCglibCopier031207500  004%  pureCglibCopier105254600  014%  hutoolCopier022156300  003%  springBeanCopier006054700  001%  mapStruct1w -------- cost: StopWatch '': running time = 601845500 ns---------------------------------------------ns         %     Task name---------------------------------------------494895600  082%  apacheCopier009014500  001%  springCglibCopier008998600  001%  pureCglibCopier067145800  011%  hutoolCopier016557700  003%  springBeanCopier005233300  001%  mapStruct10w -------- cost: StopWatch '': running time = 5543094200 ns---------------------------------------------ns         %     Task name---------------------------------------------4474871900  081%  apacheCopier089066500  002%  springCglibCopier090526400  002%  pureCglibCopier667986400  012%  hutoolCopier166274800  003%  springBeanCopier054368200  001%  mapStruct50w -------- cost: StopWatch '': running time = 27527708400 ns---------------------------------------------ns         %     Task name---------------------------------------------22145604900  080%  apacheCopier452946700  002%  springCglibCopier448455700  002%  pureCglibCopier3365908800  012%  hutoolCopier843306700  003%  springBeanCopier271485600  001%  mapStruct

II. 其余

1. 一灰灰Blog： https://liuyueyi.github.io/he...

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2. 申明

尽信书则不如，以上内容，纯属一家之言，因集体能力无限，不免有疏漏和谬误之处，如发现bug或者有更好的倡议，欢送批评指正，不吝感谢

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