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This article mainly explains "how to implement Bean copy framework underscore hump mutual extension support", the explanation content in this article is simple and clear, easy to learn and understand, please follow the idea of Xiaobian slowly in-depth, together to study and learn "how to implement Bean copy framework underscore hump mutual extension support"!

I. Support for copy

The above use is the most basic use posture, attribute name + type is consistent, there are getter/setter methods, our actual business scenario, there is a more important place, is the conversion support between underscore and hump, if you want to use the above framework, how can you adapt?

1. cglib to cglib

Spring cglib package and pure version of the cglib implementation logic is not much different, mainly in the spring inside some cache, so the performance will be relatively good; in order to be more general, here is a pure version of the cglib extension demonstration

cglib implements the core logic of the transformation in net.sf.cglib.beans.beanCopier.Generator.generateClass

public void generateClass(ClassVisitor v) { // ... Omit irrelevant code PropertyDescriptor[] getters = ReflectUtils.getBeanGetters(source); PropertyDescriptor[] setters = ReflectUtils.getBeanSetters(target); //scan all getter methods of source, write to map, key is the attribute name; //In order to support humps and underscores, we can extend this map. If the attribute name is underlined, add an extra hump kv. 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]; // 这里根据target的属性名，获取source对应的getter方法，同样适配一下，如果下划线格式的获取不到，则改用驼峰的试一下 PropertyDescriptor getter = (PropertyDescriptor)names.get(setter.getName()); if (getter != null) { // .... } } // ...} 改造逻辑，上面的注释中已经贴出来了，核心实现就比较简单了 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; }}

Then customize a PureCglibBeanCopier, copy the code before BeanCopier, and then change the two places above (complete code reference project source code)

public void generateClass(ClassVisitor v) { // ... Omit irrelevant code PropertyDescriptor[] setters = ReflectUtils.getBeanSetters(target); //scan all getter methods of source, write to map, key is the attribute name; //In order to support humps and underscores, we can extend this map. If the attribute name is underlined, add an extra hump kv. Map names = buildGetterNameMapper(source) // ... for (int i = 0; i

< setters.length; i++) { PropertyDescriptor setter = setters[i]; // 这里根据target的属性名，获取source对应的getter方法，同样适配一下，如果下划线格式的获取不到，则改用驼峰的试一下 PropertyDescriptor getter = loadSourceGetter(names, setter); if (getter != null) { // .... } } // ...}/** * 获取目标的getter方法，支持下划线与驼峰 * * @param source * @return */public Map buildGetterNameMapper(Class source) { PropertyDescriptor[] getters = org.springframework.cglib.core.ReflectUtils.getBeanGetters(source); Map 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)) { // 支持下划线转驼峰 names.put(camelName, getters[i]); } } return names;}/** * 根据target的setter方法，找到source的getter方法，支持下划线与驼峰的转换 * * @param names * @param setter * @return */public PropertyDescriptor loadSourceGetter(Map names, PropertyDescriptor setter) { String setterName = setter.getName(); return names.getOrDefault(setterName, names.get(StrUtil.toCamelCase(setterName)));} 使用姿势和之前没有什么区别，就是BeanCopier的创建这里稍稍修改一下即可（BeanCopier可以加缓存，避免频繁的创建） public T copyAndParse(K source, Class target) throws IllegalAccessException, InstantiationException { // todo copier 可以缓存起来，避免每次重新创建 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也支持下划线与驼峰的互转，而且不需要修改源码， 只用我们自己维护一个FieldMapper即可，改动成本较小；而且在map2bean, bean2map时，可以无修改的实现驼峰下划线互转，这一点还是非常很优秀的 /** * 驼峰转换 * * @param source * @param target * @param * @param * @return */public T copyAndParse(K source, Class 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（注意这个是HuTool的类，不是Cglib的）private Map cacheMap = new HashMap();private CopyOptions getCopyOptions(Class source) { CopyOptions options = cacheMap.get(source); if (options == null) { // 不加锁，我们认为重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 buildFieldMapper(Class source) { PropertyDescriptor[] properties = ReflectUtils.getBeanProperties(source); Map 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 最后再介绍一下MapStruct，虽然我们需要手动编码来实现转换，但是好处是性能高啊，既然已经手动编码了，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 接下来测试一下上面三个是否能正常工作 定义一个Target2，注意它与Source有两个字段不同，分别是 user_name/userName, marketPrice/market_price @Datapublic class Target2 { private Integer id; private String userName; private Double price; private List 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);} 输出结果如下 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 void autoCheck2(Class 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());}

The comparison is as follows, although cglib, hutool supports hump, underscore rotation, the final performance is not much different from the above

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 Thank you for reading, the above is "how to achieve Bean copy framework underscore hump mutual extension support" content, after the study of this article, I believe we have a deeper understanding of how to achieve Bean copy framework underscore hump mutual extension support, the specific use of the situation also needs to be verified. Here is, Xiaobian will push more articles related to knowledge points for everyone, welcome to pay attention!

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