<resultMap id="BaseResultMap" type="com.elim.learn.mybatis.model.SysWfProcess">

   <id column="id" jdbcType="INTEGER" property="id" />

   <result column="template_id" jdbcType="INTEGER" property="templateId" />

   <result column="creator" jdbcType="INTEGER" property="creator" />

   <result column="create_time" jdbcType="TIMESTAMP" property="createTime" />

   <collection property="nodes" column="id"

    ofType="com.elim.learn.mybatis.model.SysWfNode" select="selectNodes" fetchType="lazy"/>

  </resultMap>

  <resultMap id="SysWfNodeResult" type="com.elim.learn.mybatis.model.SysWfNode">

   <id column="id" jdbcType="INTEGER" property="nodeId" />

   <result column="process_id" jdbcType="INTEGER" property="processId" />

   <result column="node_code" jdbcType="VARCHAR" property="nodeCode" />

   <result column="node_name" jdbcType="VARCHAR" property="nodeName" />

  </resultMap>

  <select id="selectByPrimaryKey" parameterType="java.lang.Integer"

   resultMap="BaseResultMap">

   select

   <include refid="Base_Column_List" />

   from sys_wf_process

   where id = #{id,jdbcType=INTEGER}

  </select>

  <select id="selectNodes"

   resultMap="SysWfNodeResult">

   select id, process_id, node_code, node_name from sys_wf_node

   where process_id=#{id}

  </select>

   <setting name="lazyLoadingEnabled" value="true"/>

 private Object createResultObject(ResultSetWrapper rsw, ResultMap resultMap, ResultLoaderMap lazyLoader, String columnPrefix) throws SQLException {

  final List<Class<? constructorArgTypes = new ArrayList<Class<?();

  final List<Object> constructorArgs = new ArrayList<Object>();

  final Object resultObject = createResultObject(rsw, resultMap, constructorArgTypes, constructorArgs, columnPrefix);

  if (resultObject != null && !typeHandlerRegistry.hasTypeHandler(resultMap.getType())) {

   final List<ResultMapping> propertyMappings = resultMap.getPropertyResultMappings();

   for (ResultMapping propertyMapping : propertyMappings) {

    // issue gcode #109 && issue #149

    if (propertyMapping.getNestedQueryId() != null && propertyMapping.isLazy()) {

     return configuration.getProxyFactory().createProxy(resultObject, lazyLoader, configuration, objectFactory, constructorArgTypes, constructorArgs);

    }

   }

  }

  return resultObject;

 }

   <setting name="proxyFactory" value="CGLIB"/>

 @Test

  public void testLazyLoad1() {

   SysWfProcessMapper mapper = this.session.getMapper(SysWfProcessMapper.class);

   SysWfProcess process = mapper.selectByPrimaryKey(1);

   System.out.println(process.getClass());

  }
 

2016-12-23 15:43:21,131 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Preparing: select id, template_id, creator, create_time from sys_wf_process where id = "htmlcode">

  <setting name="aggressiveLazyLoading" value="fasle"/>



1.4     lazyLoadTriggerMethods
       那如果我们设置了aggressiveLazyLoading=”false”，但又希望在调用某些方法之前把所有的延迟对象都从数据库加载出来，怎么办呢？这个时候我们可以通过lazyLoadTriggerMethods参数来指定需要加载延迟对象的方法调用。默认是equals、clone、hashCode和toString，也就是说我们在调用代理对象的这些方法之前就会把延迟加载对象从数据库加载出来。


   <setting name="lazyLoadTriggerMethods" value="equals,clone,hashCode,toString" />



       Mybatis延迟加载生成的代理对象的代理过程，可以参考ProxyFactory的创建代理对象的过程，以下是基于Javassist创建的代理对象的代理过程，基于CGLIB的代理也是类似的。从下面的代码我们可以看到Mybatis的代理对象需要从数据库加载延迟对象时是在目标方法被调用以前发生的，这就可以保证我们的目标方法被调用时延迟加载的对象已经从数据库中加载出来了。


@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)) {

      Object original = null;

      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 {

      if (lazyLoader.size() > 0 && !FINALIZE_METHOD.equals(methodName)) {

       if (aggressive || lazyLoadTriggerMethods.contains(methodName)) {

        lazyLoader.loadAll();

       } else if (PropertyNamer.isProperty(methodName)) {

        final String property = PropertyNamer.methodToProperty(methodName);

        if (lazyLoader.hasLoader(property)) {

         lazyLoader.load(property);

        }

       }

      }

     }

    }

    return methodProxy.invoke(enhanced, args);

   } catch (Throwable t) {

    throw ExceptionUtil.unwrapThrowable(t);

   }

  }

 }




       本文是介绍的都是基于<collection>这种关联，其实<association>关联的对象的延迟加载也是一样的，它们的默认策略也是一样的。
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