Mybatis一般按照分析来说，可以按照三步曲进行

1、xml解析对应的配置文件

2、将配置文件通过XMLConfigBuilder解析生成Configuration对象。

3、SqlSessionFactoryBuilder通过builder方法将Configuration对象存入到里面。

4、configuration委托给MapperRegistry:运用动态代理生成对应的Dao对象.然后拿到配置文件中对应的id的sql语句，利用SqlSession执行相应的操作。

 

一般面试会问mybatis的接口是怎么实现的，其原理就是用采用jdk的动态代理来实现的，只是它的接口并没有实现类，动态代理的invoke方法中得到当前的method方法去构造MapperMethod对象，看具体代码：

public 
     
       T getMapper(Class
      
        type, SqlSession sqlSession) {    return this.mapperRegistry.getMapper(type, sqlSession);}
      
     

通过mapperregistry获取对应的对象，进一步看看getMapper的代码：

public 
     
       T getMapper(Class
      
        type, SqlSession sqlSession) {    MapperProxyFactory mapperProxyFactory = (MapperProxyFactory)this.knownMappers.get(type);    if(mapperProxyFactory == null) {        throw new BindingException("Type " + type + " is not known to the MapperRegistry.");    } else {        try {            return mapperProxyFactory.newInstance(sqlSession);        } catch (Exception var5) {            throw new BindingException("Error getting mapper instance. Cause: " + var5, var5);        }    }}
      
     

可以看到，动态代理开始了，通过代理来产生对应的对象，但是mybatis的代理是接口的，并没有实现，不要忘记哦，来看看具体的代码：

protected T newInstance(MapperProxy
     
       mapperProxy) {    return Proxy.newProxyInstance(this.mapperInterface.getClassLoader(), new Class[]{
   this.mapperInterface}, mapperProxy); //动态代理模式生成对应的类}public T newInstance(SqlSession sqlSession) {    MapperProxy mapperProxy = new MapperProxy(sqlSession, this.mapperInterface, this.methodCache);    return this.newInstance(mapperProxy);}
     

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {    try {        if(Object.class.equals(method.getDeclaringClass())) {            return method.invoke(this, args);        }        if(this.isDefaultMethod(method)) {            return this.invokeDefaultMethod(proxy, method, args);        }    } catch (Throwable var5) {        throw ExceptionUtil.unwrapThrowable(var5);    }     //这里去拿到对应的sql语句    MapperMethod mapperMethod = this.cachedMapperMethod(method);    return mapperMethod.execute(this.sqlSession, args);}

在来看看MapperMethod中的execute的方法：

public Object execute(SqlSession sqlSession, Object[] args) {    Object param;    Object result;    switch(null.$SwitchMap$org$apache$ibatis$mapping$SqlCommandType[this.command.getType().ordinal()]) {    case 1:        param = this.method.convertArgsToSqlCommandParam(args);        result = this.rowCountResult(sqlSession.insert(this.command.getName(), param));        break;    case 2:        param = this.method.convertArgsToSqlCommandParam(args);        result = this.rowCountResult(sqlSession.update(this.command.getName(), param));        break;    case 3:        param = this.method.convertArgsToSqlCommandParam(args);        result = this.rowCountResult(sqlSession.delete(this.command.getName(), param));        break;    case 4:        if(this.method.returnsVoid() && this.method.hasResultHandler()) {            this.executeWithResultHandler(sqlSession, args);            result = null;        } else if(this.method.returnsMany()) {            result = this.executeForMany(sqlSession, args);        } else if(this.method.returnsMap()) {            result = this.executeForMap(sqlSession, args);        } else if(this.method.returnsCursor()) {            result = this.executeForCursor(sqlSession, args);        } else {            param = this.method.convertArgsToSqlCommandParam(args);            result = sqlSession.selectOne(this.command.getName(), param);        }        break;    case 5:        result = sqlSession.flushStatements();        break;    default:        throw new BindingException("Unknown execution method for: " + this.command.getName());    }    if(result == null && this.method.getReturnType().isPrimitive() && !this.method.returnsVoid()) {        throw new BindingException("Mapper method \'" + this.command.getName() + " attempted to return null from a method with a primitive return type (" + this.method.getReturnType() + ").");    } else {        return result;    }}

可以看到，最终还是通过SqlSession来执行增删查改。