Mybatis[5] - 配置文件 - objectFactory

博由ObjectFactory 使用解析 默认配置对象创建使用情况 案例 创建自定义ObjectFactory配置objectFactory单元测试测试结果 总结项目地址

博由

objectFactory对象工厂，在mybatis的对象创建是通过objectFactory完成的。缺省的实现是DefaultObjectFactory，如果想实现自己的ObjectFactory可以实现ObjectFactory或者继承DefaultObjectFactory。

ObjectFactory 使用解析

默认配置

Configuration.java

protected ObjectFactory objectFactory = new DefaultObjectFactory();

XmlConfigBuilder.java

private void objectFactoryElement(XNode context) throws Exception { if (context != null) { // 如果objectFactory设置，那么覆盖DefaultObjectFactory String type = context.getStringAttribute("type"); Properties properties = context.getChildrenAsProperties(); ObjectFactory factory = (ObjectFactory) resolveClass(type).newInstance(); factory.setProperties(properties); configuration.setObjectFactory(factory); } }

DefaultObjectFactory.java

1. create: 创建对象 2. setProperties: 设置属性 3. isCollection: 是否是集合对象 DefaultObjectFactory提供了基本的创建对象的方法和解析方式。

对象创建使用情况

DefaultResultSetHandler 类中频繁的使用了DefaultObjectFactory相关方法，用于创建对象。 例如： DefaultResultHandler defaultResultHandler = new DefaultResultHandler(objectFactory); 基本使用了objectFactory.create(type);

案例

1. 创建自定义ObjectFactory

package com.objectfactory.factorys; import com.objectfactory.pojo.User; import org.apache.ibatis.reflection.factory.DefaultObjectFactory; import org.apache.ibatis.reflection.factory.ObjectFactory; import java.util.*; /** * 一般通过继承DefaultObjectFactory来自定义ObjectFactory * Created by wangzhiping on 17/3/12. */ public class TestObjectFactory extends DefaultObjectFactory { /** * 设置属性 * @param properties */ @Override public void setProperties(Properties properties) { Set<Object> keys = properties.keySet(); for(Iterator<Object> i = keys.iterator(); i.hasNext();) { System.out.println(" ====== " + properties.get(i.next()) + " ====== "); } super.setProperties(properties); } /** * 创建对象 * @param type * @return */ @Override public Object create(Class type) { if (type.equals(User.class)){ User user = (User)super.create(type); user.setName("---create---"); user.setCreatedAt(new Date()); return user; } return super.create(type); } /** * 创建对象根据指定的参数对象 * @param type * @param constructorArgTypes * @param constructorArgs * @param <T> * @return */ @Override public <T> T create(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) { return super.create(type, constructorArgTypes, constructorArgs); } /** * 判断是否是集合 * @param type * @param <T> * @return */ @Override public <T> boolean isCollection(Class<T> type) { return super.isCollection(type); } }

2. 配置objectFactory

<objectFactory type="com.objectfactory.factorys.TestObjectFactory" > <property name="username" value="wangzhiping" /> <property name="password" value="wangzhiping" /> </objectFactory>

3. 单元测试

@Test public void testObjectFactory() { SqlSession session = instance.getSession(); User user = session.selectOne(User.class.getName() + ".findById", 5); System.out.println(user); }

4. 测试结果

====== wangzhiping ====== ====== wangzhiping ====== Logging initialized using 'class org.apache.ibatis.logging.stdout.StdOutImpl' adapter. PooledDataSource forcefully closed/removed all connections. PooledDataSource forcefully closed/removed all connections. PooledDataSource forcefully closed/removed all connections. PooledDataSource forcefully closed/removed all connections. Opening JDBC Connection Created connection 1073533248. Setting autocommit to false on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@3ffcd140] ==> Preparing: SELECT * FROM user WHERE id = ? ==> Parameters: 5(Integer) <== Columns: id, name, created_at, updated_at <== Row: 5, admin, 2017-02-20 02:32:37, 2017-02-20 02:32:37 <== Total: 1 User{id=5, name='admin', createdAt=Sun Mar 12 16:57:45 CST 2017, updatedAt=null} ----------------------------------------------------- 1. 属性来源于<objectFactory>中的<property>标签设置； 2. User->created_at属性，是通过create创建对象时，赋值结果；

总结

个人认为一般很少会使用到自定义ObjectFactory，如果需要使用的话，建议是在对象创建时需要做一些操作，或前或后，用于改变或者丰富被创建对象。

项目地址:

branch v1.5: https://github.com/wzpthq/csdn_mybatis.git