因为通过javassist和cglib代理实现的，所以说到底最主要的就是JavasisstProxyFactory类中的invoke方法和里面的load方法。

其实读一读，里面的逻辑就是跟配置中定义的规则一样的
因为github上的mybatis中文版中这部分注释比较少，所以从网上寻找博客，截取了代码注释片段记录下。
JavasisstProxyFactory

public class JavassistProxyFactory implements org.apache.ibatis.executor.loader.ProxyFactory { /** * 接口实现 * @param target 目标结果对象 * @param lazyLoader 延迟加载对象 * @param configuration 配置 * @param objectFactory 对象工厂 * @param constructorArgTypes 构造参数类型 * @param constructorArgs 构造参数值 * @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... /** * 代理对象实现，核心逻辑执行 */ private static class EnhancedResultObjectProxyImpl implements MethodHandler { /** * 创建代理对象 * @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 { //通过获取对象方法，判断是否存在该方法 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) { //没找到该方法，实现接口 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 { //创建新的代理对象 enhanced = enhancer.create(typesArray, valuesArray); } catch (Exception e) { throw new ExecutorException("Error creating lazy proxy. Cause: " + e, e); } //设置代理执行器 ((Proxy) enhanced).setHandler(callback); return enhanced; } /** * 代理对象执行 * @param enhanced 原对象 * @param method 原对象方法 * @param methodProxy 代理方法 * @param args 方法参数 * @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)) { //忽略暂未找到具体作用 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 { //延迟加载数量大于0 if (lazyLoader.size() > 0 && !FINALIZE_METHOD.equals(methodName)) { //aggressive 一次加载性所有需要要延迟加载属性或者包含触发延迟加载方法 if (aggressive || lazyLoadTriggerMethods.contains(methodName)) { log.debug("==> laze lod trigger method:" + methodName + ",proxy method:" + methodProxy.getName() + " class:" + enhanced.getClass()); //一次全部加载 lazyLoader.loadAll(); } else if (PropertyNamer.isSetter(methodName)) { //判断是否为set方法，set方法不需要延迟加载 final String property = PropertyNamer.methodToProperty(methodName); lazyLoader.remove(property); } else if (PropertyNamer.isGetter(methodName)) { final String property = PropertyNamer.methodToProperty(methodName); if (lazyLoader.hasLoader(property)) { //延迟加载单个属性 lazyLoader.load(property); log.debug("load one :" + methodName); } } } } } return methodProxy.invoke(enhanced, args); } catch (Throwable t) { throw ExceptionUtil.unwrapThrowable(t); } } }

load方法

/** * 执行懒加载查询，获取数据并且set到userObject中返回 * @param userObject * @throws SQLException */ public void load(final Object userObject) throws SQLException { //合法性校验 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."); } //获取mappedstatement并且校验 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构建metaobject,并且重新构建resultloader对象 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); } //获取数据库查询结果并且set到结果对象返回 this.metaResultObject.setValue(property, this.resultLoader.loadResult()); }

参考地址：
https:///qixidi/p/10251126.html
https://blog.csdn.net/mingtian625/article/details/47358003

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