下面的例子是Student类关联一个Teacher对象，在访问Student对象时，不立即加载其关联的Teacher对象，而是等到访问Teacher对象的属性时，才加载Teacher对象。
源代码下载：
1.Student.java
package dao.domain;public class Student { public int id; public String name; public int teacher_id; public Teacher teacher; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getTeacher_id() { return teacher_id; } public void setTeacher_id(int teacher_id) { this.teacher_id = teacher_id; } public Teacher getTeacher() { return teacher; } public void setTeacher(Teacher teacher) { this.teacher = teacher; }} 2.Teacher.java
package dao.domain;public class Teacher { public int id; public String name; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } } 3.StudentDAO.java
package dao;import dao.domain.Student;public interface StudentDAO { public Student getStudentByID(int id);} 4.StudentDAOImpl.java
package dao.impl;import java.io.IOException;import java.io.Reader;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import dao.StudentDAO;import dao.domain.Student;public class StudentDaoImpl implements StudentDAO { private static SqlSession session = null; private static StudentDAO mapper = null; static{ String resouce = "config/ibatisConfiguration.xml"; Reader reader = null; try { reader = Resources.getResourceAsReader(resouce); } catch (IOException e) { e.printStackTrace(); } SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader); session = factory.openSession(); mapper = session.getMapper(StudentDAO.class); try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } @Override public Student getStudentByID(int id) { return mapper.getStudentByID(id); } } 5.TeacherMapper.xml
6.StudentMapper.xml
7.ibatisConfiguration.xml
8.测试类
import dao.StudentDAO;import dao.domain.Student;import dao.impl.StudentDaoImpl;public class Test { public static void main(String[] args) { StudentDAO dao = new StudentDaoImpl(); Student article = dao.getStudentByID(1); System.out.println(article.getTeacher().getName()); }} 9.mybatis延迟加载说明： 1）在mybatis配置文件中，配置如下两个配置项：
2）查询语句样例，下面通过association将Student对象一个属性与一个查询语句关联起来：
这样，在查询出StudentMap这个结果集时，对于teacher字段就会采取延迟加载了，等到访问teacher对象属性时，才会去加载关联的teacher对象。
10.逐步深入延迟加载细节
1）在Test类中如下行打上断点，然后进行Debug
System.out.println(article.getTeacher().getName());
可以看到article对象为（每次测试，结果会不同）：
这就是一个cglib自动生成的代理对象。
2）那这个代理对象什么时候生成的呢？ 经过反复不停的debug跟踪，得到下面这样一个调用栈。
Thread [main] (Suspended (breakpoint at line 61 in CglibProxyFactory)) CglibProxyFactory.createProxy(Object, ResultLoaderMap, Configuration, ObjectFactory, List>, List
可以看到在查询Student对象时，DefaultResultSetHandler(org\apache\ibatis\executor\resultset)类会对数据库查询的每一行结果进行封装处理。
通过下面的代码可以看得更清楚，当结果对象中存在嵌套查询时，当前对象就会被替换为一个代理对象。
private Object createResultObject(ResultSetWrapper rsw, ResultMap resultMap, ResultLoaderMap lazyLoader, String columnPrefix) throws SQLException { final List > constructorArgTypes = new ArrayList >(); final List 3）那当访问代理对象时，会发生什么事情呢？ 如调用System.out.println(article.getTeacher().getName())时，得到如下的调用栈信息
Thread [main] (Suspended (breakpoint at line 143 in CglibProxyFactory$EnhancedResultObjectProxyImpl)) owns: ResultLoaderMap (id=38) CglibProxyFactory$EnhancedResultObjectProxyImpl.intercept(Object, Method, Object[], MethodProxy) line: 143 Student$$EnhancerByCGLIB$$e1afda28.getTeacher() line: not available Test.main(String[]) line: 10
代码执行到了如下地方：
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); } } } 通过调用lazyLoader.loadAll来对需要加载的对象进行加载.
继续顺藤摸瓜，得到如下的调用栈：
Thread [main] (Suspended) owns: ResultLoaderMap (id=38) BeanWrapper.set(PropertyTokenizer, Object) line: 57 MetaObject.setValue(String, Object) line: 133 ResultLoaderMap$LoadPair.load(Object) line: 207 ResultLoaderMap$LoadPair.load() line: 172 ResultLoaderMap.load(String) line: 80 ResultLoaderMap.loadAll() line: 90 CglibProxyFactory$EnhancedResultObjectProxyImpl.intercept(Object, Method, Object[], MethodProxy) line: 143 Student$$EnhancerByCGLIB$$e1afda28.getTeacher() line: not available Test.main(String[]) line: 10
如下是BeanWrapper中setValue方法：
public void set(PropertyTokenizer prop, Object value) { if (prop.getIndex() != null) { Object collection = resolveCollection(prop, object); setCollectionValue(prop, collection, value); } else { setBeanProperty(prop, object, value); } } 通过setBeanProperty方法，就完成向Student对象设置Teacher属性的过程（上面代码中的object就是Student对象）。
下面通过一张图，展示一下代理对象与实际对象之间的关系，”为代理对象，是Student类的子类，当访问到Student的getTeacher方法时，其通过关联的EnhancedResultObjectProxyImpl类来加载teacher对象，具体关联见下图，其中BeanWrapper中object就是代理对象本身，通过对object的设置，将teacher属性设置为从数据库查询出来的对象，完成延迟加载。
至此，mybatis的整个延迟加载过程就分析完了。