因?yàn)橥ㄟ^(guò)javassist和cglib代理實(shí)現(xiàn)的，所以說(shuō)到底最主要的就是JavasisstProxyFactory類中的invoke方法和里面的load方法。

其實(shí)讀一讀，里面的邏輯就是跟配置中定義的規(guī)則一樣的因?yàn)間ithub上的mybatis中文版中這部分注釋比較少，所以從網(wǎng)上尋找博客，截取了代碼注釋片段記錄下。JavasisstProxyFactory

public class JavassistProxyFactory implements org.apache.ibatis.executor.loader.ProxyFactory { /** * 接口實(shí)現(xiàn) * @param target 目標(biāo)結(jié)果對(duì)象 * @param lazyLoader 延遲加載對(duì)象 * @param configuration 配置 * @param objectFactory 對(duì)象工廠 * @param constructorArgTypes 構(gòu)造參數(shù)類型 * @param constructorArgs 構(gòu)造參數(shù)值 * @return */ @Override public Object createProxy(Object target, ResultLoaderMap lazyLoader, Configuration configuration, ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) { return EnhancedResultObjectProxyImpl.createProxy(target, lazyLoader, configuration, objectFactory, constructorArgTypes, constructorArgs); } //省略... /** * 代理對(duì)象實(shí)現(xiàn)，核心邏輯執(zhí)行 */ private static class EnhancedResultObjectProxyImpl implements MethodHandler { /** * 創(chuàng)建代理對(duì)象 * @param type * @param callback * @param constructorArgTypes * @param constructorArgs * @return */ static Object crateProxy(Class<?> type, MethodHandler callback, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) { ProxyFactory enhancer = new ProxyFactory(); enhancer.setSuperclass(type); try { //通過(guò)獲取對(duì)象方法，判斷是否存在該方法 type.getDeclaredMethod(WRITE_REPLACE_METHOD); // ObjectOutputStream will call writeReplace of objects returned by writeReplace if (log.isDebugEnabled()) { log.debug(WRITE_REPLACE_METHOD + " method was found on bean " + type + ", make sure it returns this"); } } catch (NoSuchMethodException e) { //沒找到該方法，實(shí)現(xiàn)接口 enhancer.setInterfaces(new Class[]{WriteReplaceInterface.class}); } catch (SecurityException e) { // nothing to do here } Object enhanced; Class<?>[] typesArray = constructorArgTypes.toArray(new Class[constructorArgTypes.size()]); Object[] valuesArray = constructorArgs.toArray(new Object[constructorArgs.size()]); try { //創(chuàng)建新的代理對(duì)象 enhanced = enhancer.create(typesArray, valuesArray); } catch (Exception e) { throw new ExecutorException("Error creating lazy proxy. Cause: " + e, e); } //設(shè)置代理執(zhí)行器 ((Proxy) enhanced).setHandler(callback); return enhanced; } /** * 代理對(duì)象執(zhí)行 * @param enhanced 原對(duì)象 * @param method 原對(duì)象方法 * @param methodProxy 代理方法 * @param args 方法參數(shù) * @return * @throws Throwable */ @Override public Object invoke(Object enhanced, Method method, Method methodProxy, Object[] args) throws Throwable { final String methodName = method.getName(); try { synchronized (lazyLoader) { if (WRITE_REPLACE_METHOD.equals(methodName)) { //忽略暫未找到具體作用 Object original; if (constructorArgTypes.isEmpty()) { original = objectFactory.create(type); } else { original = objectFactory.create(type, constructorArgTypes, constructorArgs); } PropertyCopier.copyBeanProperties(type, enhanced, original); if (lazyLoader.size() > 0) { return new JavassistSerialStateHolder(original, lazyLoader.getProperties(), objectFactory, constructorArgTypes, constructorArgs); } else { return original; } } else { //延遲加載數(shù)量大于0 if (lazyLoader.size() > 0 && !FINALIZE_METHOD.equals(methodName)) { //aggressive 一次加載性所有需要要延遲加載屬性或者包含觸發(fā)延遲加載方法 if (aggressive || lazyLoadTriggerMethods.contains(methodName)) { log.debug("==> laze lod trigger method:" + methodName + ",proxy method:" + methodProxy.getName() + " class:" + enhanced.getClass()); //一次全部加載 lazyLoader.loadAll(); } else if (PropertyNamer.isSetter(methodName)) { //判斷是否為set方法，set方法不需要延遲加載 final String property = PropertyNamer.methodToProperty(methodName); lazyLoader.remove(property); } else if (PropertyNamer.isGetter(methodName)) { final String property = PropertyNamer.methodToProperty(methodName); if (lazyLoader.hasLoader(property)) { //延遲加載單個(gè)屬性 lazyLoader.load(property); log.debug("load one :" + methodName); } } } } } return methodProxy.invoke(enhanced, args); } catch (Throwable t) { throw ExceptionUtil.unwrapThrowable(t); } } }

load方法

/** * 執(zhí)行懶加載查詢，獲取數(shù)據(jù)并且set到userObject中返回 * @param userObject * @throws SQLException */ public void load(final Object userObject) throws SQLException { //合法性校驗(yàn) if (this.metaResultObject == null || this.resultLoader == null) { if (this.mappedParameter == null) { throw new ExecutorException('Property [' + this.property + '] cannot be loaded because ' + 'required parameter of mapped statement [' + this.mappedStatement + '] is not serializable.'); } //獲取mappedstatement并且校驗(yàn) final Configuration config = this.getConfiguration(); final MappedStatement ms = config.getMappedStatement(this.mappedStatement); if (ms == null) { throw new ExecutorException('Cannot lazy load property [' + this.property + '] of deserialized object [' + userObject.getClass() + '] because configuration does not contain statement [' + this.mappedStatement + ']'); } //使用userObject構(gòu)建metaobject,并且重新構(gòu)建resultloader對(duì)象 this.metaResultObject = config.newMetaObject(userObject); this.resultLoader = new ResultLoader(config, new ClosedExecutor(), ms, this.mappedParameter, metaResultObject.getSetterType(this.property), null, null); } /* We are using a new executor because we may be (and likely are) on a new thread * and executors aren’t thread safe. (Is this sufficient?) * * A better approach would be making executors thread safe. */ if (this.serializationCheck == null) { final ResultLoader old = this.resultLoader; this.resultLoader = new ResultLoader(old.configuration, new ClosedExecutor(), old.mappedStatement, old.parameterObject, old.targetType, old.cacheKey, old.boundSql); } //獲取數(shù)據(jù)庫(kù)查詢結(jié)果并且set到結(jié)果對(duì)象返回 this.metaResultObject.setValue(property, this.resultLoader.loadResult()); }

參考地址：https://www.cnblogs.com/qixidi/p/10251126.htmlhttps://blog.csdn.net/mingtian625/article/details/47358003

到此這篇關(guān)于Mybatis懶加載的實(shí)現(xiàn)的文章就介紹到這了,更多相關(guān)Mybatis 懶加載內(nèi)容請(qǐng)搜索好吧啦網(wǎng)以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持好吧啦網(wǎng)！