如何實現(xiàn)Mybatis懶加載

public class JavassistProxyFactory implements org.apache.ibatis.executor.loader.ProxyFactory {

 
 /**
 * 接口實現(xiàn)
 * @param target 目標(biāo)結(jié)果對象
 * @param lazyLoader 延遲加載對象
 * @param configuration 配置
 * @param objectFactory 對象工廠
 * @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...
 
 /**
 * 代理對象實現(xiàn)，核心邏輯執(zhí)行
 */
 private static class EnhancedResultObjectProxyImpl implements MethodHandler {
 
 /**
 * 創(chuàng)建代理對象
 * @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 {
  //通過獲取對象方法，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;
 }
 
 
  /**
  * 代理對象執(zhí)行
  * @param enhanced 原對象
  * @param method 原對象方法
  * @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)) {
     //延遲加載單個屬性
     lazyLoader.load(property);
     log.debug("load one :" + methodName);
    }
    }
   }
   }
  }
  return methodProxy.invoke(enhanced, args);
  } catch (Throwable t) {
  throw ExceptionUtil.unwrapThrowable(t);
  }
 }
 }

/**
  * 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
  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
  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)庫查詢結(jié)果并且set到結(jié)果對象返回
  this.metaResultObject.setValue(property, this.resultLoader.loadResult());
 }