Mybatis源码学习之反射工具（三）

ゞ浴缸里的玫瑰 2022-05-23 13:52 258阅读 0赞

### 简述 ###

MyBatis在进行参数处理、结果映射等操作时，会涉及大量的反射操作。Java中的反射虽然功能强大，但是代码编写起来比较复杂且容易出错，为了简化反射操作的相关代码，MyBatis提供了专门的反射模块，该模块位于org.apache.ibatis.reflection包中，它对常见的反射操作做了进一步封装，提供了更加简洁方便的反射API。

### Reflector & ReflectorFactory ###

**Reflector**

Reflector是MyBatis中反射模块的基础，每个Reflector对象都对应一个类，在Reflector中缓存了反射操作需要使用的类的元信息。Reflector 中各个字段的含义如下：

/** * 缓存了反射操作需要使用的类的元信息。 * 允许在属性名和getter/setter方法之间轻松映射 * * @author Clinton Begin */
    public class Reflector { 
    
        /** * 对应Class类型 */
        private final Class<?> type;
        /** * 可读属性的名称集合，可读属性就是存在相应getter方法的属性，初始值为空数组 */
        private final String[] readablePropertyNames;
        /** * 可写属性的名称集合，可写属性就是存在相应setter方法的属性，初始值为空数组 */
        private final String[] writeablePropertyNames;
        /** * 记录了属性相应的setter方法，key是属性名称，value是Invoker对象，它是对setter方法对应Method对象的封装， */
        private final Map<String, Invoker> setMethods = new HashMap<String, Invoker>();
        /** * 属性相应的getter方法集合，key是属性名称，value也是Invoker对象 * <p> */
        private final Map<String, Invoker> getMethods = new HashMap<String, Invoker>();
        /** * 记录了属性相应的setter方法的参数值类型，key是属性名称，value是setter方法的参数类型 */
        private final Map<String, Class<?>> setTypes = new HashMap<String, Class<?>>();
        /** * 记录了属性相应的getter方法的返回值类型，key是属性名称，value是getter方法的返回值类型 */
        private final Map<String, Class<?>> getTypes = new HashMap<String, Class<?>>();
        /** * 记录了默认构造方法 */
        private Constructor<?> defaultConstructor;
        /** * 记录了所有属性名称集合 */
        private Map<String, String> caseInsensitivePropertyMap = new HashMap<String, String>();
    
        /** * 构造函数，对上述字段初始化 */
        public Reflector(Class<?> clazz) {
            type = clazz;
            addDefaultConstructor(clazz);
            addGetMethods(clazz);
            addSetMethods(clazz);
            addFields(clazz);
            readablePropertyNames = getMethods.keySet().toArray(new String[getMethods.keySet().size()]);
            writeablePropertyNames = setMethods.keySet().toArray(new String[setMethods.keySet().size()]);
            for (String propName : readablePropertyNames) {
                caseInsensitivePropertyMap.put(propName.toUpperCase(Locale.ENGLISH), propName);
            }
            for (String propName : writeablePropertyNames) {
                caseInsensitivePropertyMap.put(propName.toUpperCase(Locale.ENGLISH), propName);
            }
        }
    
        /** * 获取指定Class对象的默认构造方法（包括无参构造方法） */
        private void addDefaultConstructor(Class<?> clazz) {
            Constructor<?>[] consts = clazz.getDeclaredConstructors();
            for (Constructor<?> constructor : consts) {
                //默认构造方法没有参数
                if (constructor.getParameterTypes().length == 0) {
                    //允许利用反射检查任意类的私有变量
                    if (canAccessPrivateMethods()) {
                        try {
                            constructor.setAccessible(true);
                        } catch (Exception e) {
                            // Ignored. This is only a final precaution, nothing we can do.
                        }
                    }
                    if (constructor.isAccessible()) {
                        this.defaultConstructor = constructor;
                    }
                }
            }
        }
    
        /** * 负责解析类中定义的getter方法 */
        private void addGetMethods(Class<?> cls) {
            Map<String, List<Method>> conflictingGetters = new HashMap<String, List<Method>>();
            Method[] methods = getClassMethods(cls);
            for (Method method : methods) {
                if (method.getParameterTypes().length > 0) {
                    continue;
                }
                String name = method.getName();
                if ((name.startsWith("get") && name.length() > 3)
                        || (name.startsWith("is") && name.length() > 2)) {
                    //获取字段名
                    name = PropertyNamer.methodToProperty(name);
                    addMethodConflict(conflictingGetters, name, method);
                }
            }
            resolveGetterConflicts(conflictingGetters);
        }
    
        private void resolveGetterConflicts(Map<String, List<Method>> conflictingGetters) {
            //遍历conflictingGetters集合
            for (Entry<String, List<Method>> entry : conflictingGetters.entrySet()) {
                Method winner = null;
                //获取属性名
                String propName = entry.getKey();
                for (Method candidate : entry.getValue()) {
                    if (winner == null) {
                        winner = candidate;
                        continue;
                    }
                    Class<?> winnerType = winner.getReturnType();
                    Class<?> candidateType = candidate.getReturnType();
                    if (candidateType.equals(winnerType)) {
                        if (!boolean.class.equals(candidateType)) {
                            throw new ReflectionException(
                                    "Illegal overloaded getter method with ambiguous type for property "
                                            + propName + " in class " + winner.getDeclaringClass()
                                            + ". This breaks the JavaBeans specification and can cause unpredictable results.");
                        } else if (candidate.getName().startsWith("is")) {
                            winner = candidate;
                        }
                    } else if (candidateType.isAssignableFrom(winnerType)) {
                        // OK getter type is descendant
                    } else if (winnerType.isAssignableFrom(candidateType)) {
                        winner = candidate;
                    } else {
                        //返回值相同，存在二义性，抛出异常
                        throw new ReflectionException(
                                "Illegal overloaded getter method with ambiguous type for property "
                                        + propName + " in class " + winner.getDeclaringClass()
                                        + ". This breaks the JavaBeans specification and can cause unpredictable results.");
                    }
                }
                addGetMethod(propName, winner);
            }
        }
    
        /** * 收集get方法 */
        private void addGetMethod(String name, Method method) {
            if (isValidPropertyName(name)) {
                getMethods.put(name, new MethodInvoker(method));
                Type returnType = TypeParameterResolver.resolveReturnType(method, type);
                getTypes.put(name, typeToClass(returnType));
            }
        }
    
        /** * 收集set方法 */
        private void addSetMethods(Class<?> cls) {
            Map<String, List<Method>> conflictingSetters = new HashMap<String, List<Method>>();
            Method[] methods = getClassMethods(cls);
            for (Method method : methods) {
                String name = method.getName();
                if (name.startsWith("set") && name.length() > 3) {
                    if (method.getParameterTypes().length == 1) {
                        name = PropertyNamer.methodToProperty(name);
                        addMethodConflict(conflictingSetters, name, method);
                    }
                }
            }
            resolveSetterConflicts(conflictingSetters);
        }
    
        private void addMethodConflict(Map<String, List<Method>> conflictingMethods, String name, Method method) {
            List<Method> list = conflictingMethods.get(name);
            if (list == null) {
                list = new ArrayList<Method>();
                conflictingMethods.put(name, list);
            }
            list.add(method);
        }
    
        private void resolveSetterConflicts(Map<String, List<Method>> conflictingSetters) {
            for (String propName : conflictingSetters.keySet()) {
                List<Method> setters = conflictingSetters.get(propName);
                Class<?> getterType = getTypes.get(propName);
                Method match = null;
                ReflectionException exception = null;
                for (Method setter : setters) {
                    Class<?> paramType = setter.getParameterTypes()[0];
                    if (paramType.equals(getterType)) {
                        // should be the best match
                        match = setter;
                        break;
                    }
                    if (exception == null) {
                        try {
                            match = pickBetterSetter(match, setter, propName);
                        } catch (ReflectionException e) {
                            // there could still be the 'best match'
                            match = null;
                            exception = e;
                        }
                    }
                }
                if (match == null) {
                    throw exception;
                } else {
                    addSetMethod(propName, match);
                }
            }
        }
    
        private Method pickBetterSetter(Method setter1, Method setter2, String property) {
            if (setter1 == null) {
                return setter2;
            }
            Class<?> paramType1 = setter1.getParameterTypes()[0];
            Class<?> paramType2 = setter2.getParameterTypes()[0];
            if (paramType1.isAssignableFrom(paramType2)) {
                return setter2;
            } else if (paramType2.isAssignableFrom(paramType1)) {
                return setter1;
            }
            throw new ReflectionException("Ambiguous setters defined for property '" + property + "' in class '"
                    + setter2.getDeclaringClass() + "' with types '" + paramType1.getName() + "' and '"
                    + paramType2.getName() + "'.");
        }
    
        private void addSetMethod(String name, Method method) {
            if (isValidPropertyName(name)) {
                setMethods.put(name, new MethodInvoker(method));
                Type[] paramTypes = TypeParameterResolver.resolveParamTypes(method, type);
                setTypes.put(name, typeToClass(paramTypes[0]));
            }
        }
    
        private Class<?> typeToClass(Type src) {
            Class<?> result = null;
            if (src instanceof Class) {
                result = (Class<?>) src;
            } else if (src instanceof ParameterizedType) {
                result = (Class<?>) ((ParameterizedType) src).getRawType();
            } else if (src instanceof GenericArrayType) {
                Type componentType = ((GenericArrayType) src).getGenericComponentType();
                if (componentType instanceof Class) {
                    result = Array.newInstance((Class<?>) componentType, 0).getClass();
                } else {
                    Class<?> componentClass = typeToClass(componentType);
                    result = Array.newInstance((Class<?>) componentClass, 0).getClass();
                }
            }
            if (result == null) {
                result = Object.class;
            }
            return result;
        }
    
        private void addFields(Class<?> clazz) {
            Field[] fields = clazz.getDeclaredFields();
            for (Field field : fields) {
                if (canAccessPrivateMethods()) {
                    try {
                        field.setAccessible(true);
                    } catch (Exception e) {
                        // Ignored. This is only a final precaution, nothing we can do.
                    }
                }
                if (field.isAccessible()) {
                    if (!setMethods.containsKey(field.getName())) {
                        // issue #379 - removed the check for final because JDK 1.5 allows
                        // modification of final fields through reflection (JSR-133). (JGB)
                        // pr #16 - final static can only be set by the classloader
                        int modifiers = field.getModifiers();
                        if (!(Modifier.isFinal(modifiers) && Modifier.isStatic(modifiers))) {
                            addSetField(field);
                        }
                    }
                    if (!getMethods.containsKey(field.getName())) {
                        addGetField(field);
                    }
                }
            }
            if (clazz.getSuperclass() != null) {
                addFields(clazz.getSuperclass());
            }
        }
    
        private void addSetField(Field field) {
            if (isValidPropertyName(field.getName())) {
                setMethods.put(field.getName(), new SetFieldInvoker(field));
                Type fieldType = TypeParameterResolver.resolveFieldType(field, type);
                setTypes.put(field.getName(), typeToClass(fieldType));
            }
        }
    
        private void addGetField(Field field) {
            if (isValidPropertyName(field.getName())) {
                getMethods.put(field.getName(), new GetFieldInvoker(field));
                Type fieldType = TypeParameterResolver.resolveFieldType(field, type);
                getTypes.put(field.getName(), typeToClass(fieldType));
            }
        }
    
        private boolean isValidPropertyName(String name) {
            return !(name.startsWith("$") || "serialVersionUID".equals(name) || "class".equals(name));
        }
    
        /* * 此方法返回一个数组，该数组包含该类中声明的所有方法和任何超类 * 我们使用此方法不是为了代替 Class.getMethods(), * 因为我们想访问类中的私有方法. * * @param cls Class对象 * @return 包含该类中所有方法的数组 */
        private Method[] getClassMethods(Class<?> cls) {
            //用于记录指定类中定义的全部方法的唯一签名以及对应的Method对象
            Map<String, Method> uniqueMethods = new HashMap<String, Method>();
            Class<?> currentClass = cls;
            while (currentClass != null) {
                //记录当前类中定义的所有方法
                addUniqueMethods(uniqueMethods, currentClass.getDeclaredMethods());
    
                // 记录接口中定义的方法
                Class<?>[] interfaces = currentClass.getInterfaces();
                for (Class<?> anInterface : interfaces) {
                    addUniqueMethods(uniqueMethods, anInterface.getMethods());
                }
                //当前类的父类
                currentClass = currentClass.getSuperclass();
            }
    
            Collection<Method> methods = uniqueMethods.values();
            //转换成数组返回
            return methods.toArray(new Method[methods.size()]);
        }
    
        /** * 为每个方法生成唯一签名，并记录到uniqueMethods集合中 */
        private void addUniqueMethods(Map<String, Method> uniqueMethods, Method[] methods) {
            for (Method currentMethod : methods) {
                if (!currentMethod.isBridge()) {
                    //得到方法签名
                    String signature = getSignature(currentMethod);
                    //根据方法签名排重
                    if (!uniqueMethods.containsKey(signature)) {
                        if (canAccessPrivateMethods()) {
                            try {
                                currentMethod.setAccessible(true);
                            } catch (Exception e) {
                                // Ignored. This is only a final precaution, nothing we can do.
                            }
                        }
                        //记录签名与方法的对应关系
                        uniqueMethods.put(signature, currentMethod);
                    }
                }
            }
        }
    
        /** * 获取方法签名,eg:java.lang.String#getSignature:java.lang.reflect.Method */
        private String getSignature(Method method) {
            StringBuilder sb = new StringBuilder();
            //方法返回类型
            Class<?> returnType = method.getReturnType();
            if (returnType != null) {
                sb.append(returnType.getName()).append('#');
            }
            sb.append(method.getName());
            Class<?>[] parameters = method.getParameterTypes();
            for (int i = 0; i < parameters.length; i++) {
                if (i == 0) {
                    sb.append(':');
                } else {
                    sb.append(',');
                }
                sb.append(parameters[i].getName());
            }
            return sb.toString();
        }
    
        /** * 获取访问私有方法的权限 */
        private static boolean canAccessPrivateMethods() {
            try {
                SecurityManager securityManager = System.getSecurityManager();
                if (null != securityManager) {
                    //允许利用反射检查任意类的私有变量
                    securityManager.checkPermission(new ReflectPermission("suppressAccessChecks"));
                }
            } catch (SecurityException e) {
                return false;
            }
            return true;
        }
    
        /* * Gets the name of the class the instance provides information for * * @return The class name */
        public Class<?> getType() {
            return type;
        }
    
        public Constructor<?> getDefaultConstructor() {
            if (defaultConstructor != null) {
                return defaultConstructor;
            } else {
                throw new ReflectionException("There is no default constructor for " + type);
            }
        }
    
        public boolean hasDefaultConstructor() {
            return defaultConstructor != null;
        }
    
        public Invoker getSetInvoker(String propertyName) {
            Invoker method = setMethods.get(propertyName);
            if (method == null) {
                throw new ReflectionException("There is no setter for property named '" + propertyName + "' in '" + type + "'");
            }
            return method;
        }
    
        public Invoker getGetInvoker(String propertyName) {
            Invoker method = getMethods.get(propertyName);
            if (method == null) {
                throw new ReflectionException("There is no getter for property named '" + propertyName + "' in '" + type + "'");
            }
            return method;
        }
    
        /* * Gets the type for a property setter * * @param propertyName - the name of the property * @return The Class of the propery setter */
        public Class<?> getSetterType(String propertyName) {
            Class<?> clazz = setTypes.get(propertyName);
            if (clazz == null) {
                throw new ReflectionException("There is no setter for property named '" + propertyName + "' in '" + type + "'");
            }
            return clazz;
        }
    
        /* * Gets the type for a property getter * * @param propertyName - the name of the property * @return The Class of the propery getter */
        public Class<?> getGetterType(String propertyName) {
            Class<?> clazz = getTypes.get(propertyName);
            if (clazz == null) {
                throw new ReflectionException("There is no getter for property named '" + propertyName + "' in '" + type + "'");
            }
            return clazz;
        }
    
        /* * Gets an array of the readable properties for an object * * @return The array */
        public String[] getGetablePropertyNames() {
            return readablePropertyNames;
        }
    
        /* * Gets an array of the writeable properties for an object * * @return The array */
        public String[] getSetablePropertyNames() {
            return writeablePropertyNames;
        }
    
        /* * Check to see if a class has a writeable property by name * * @param propertyName - the name of the property to check * @return True if the object has a writeable property by the name */
        public boolean hasSetter(String propertyName) {
            return setMethods.keySet().contains(propertyName);
        }
    
        /* * Check to see if a class has a readable property by name * * @param propertyName - the name of the property to check * @return True if the object has a readable property by the name */
        public boolean hasGetter(String propertyName) {
            return getMethods.keySet().contains(propertyName);
        }
    
        public String findPropertyName(String name) {
            return caseInsensitivePropertyMap.get(name.toUpperCase(Locale.ENGLISH));
        }
    }

Reflector.addGetMethods（）方法主要负责解析类中定义的getter方法，Reflector.addSetMethods（）方法负责解析类中定义的setter方法，两者的逻辑类似，具体实现见源码。

**ReflectorFactory接口**

ReflectorFactory接口主要实现了对Reflector对象的创建和缓存，该接口定义如下：

public interface ReflectorFactory { 
    
        /** * 是否会缓存Reflector对象 */
        boolean isClassCacheEnabled();
    
        /** * 设置是否缓存Reflector对象 */
        void setClassCacheEnabled(boolean classCacheEnabled);
    
        /** * 创建指定Class的Reflector对象 */
        Reflector findForClass(Class<?> type);
    }

MyBatis只为该接口提供了DefaultReflectorFactory这一个实现类，它与Reflector的关系如下：

![image][]

DefaultReflectorFactory各字段及方法的含义如下：

public class DefaultReflectorFactory implements ReflectorFactory { 
        /** * 默认开启对Reflector对象的缓存 */
        private boolean classCacheEnabled = true;
    
        /** * 使用集合ConcurrentHashMap实现对Reflector的缓存 */
        private final ConcurrentMap<Class<?>, Reflector> reflectorMap = new ConcurrentHashMap<Class<?>, Reflector>();
    
        public DefaultReflectorFactory() {
        }
    
        @Override
        public boolean isClassCacheEnabled() {
            return classCacheEnabled;
        }
    
        @Override
        public void setClassCacheEnabled(boolean classCacheEnabled) {
            this.classCacheEnabled = classCacheEnabled;
        }
    
        /** * 为指定的Class创建Reflector对象，并将Reflector对象缓存到reflectorMap中 */
        @Override
        public Reflector findForClass(Class<?> type) {
            //检查是否开启缓存
            if (classCacheEnabled) {
                // synchronized (type) removed see issue #461
                Reflector cached = reflectorMap.get(type);
                if (cached == null) {
                    //创建Reflector对象
                    cached = new Reflector(type);
                    //放入ConcurrentHashMap集合缓存
                    reflectorMap.put(type, cached);
                }
                return cached;
            } else {
                //没有开启缓存,直接创建Reflector对象并返回
                return new Reflector(type);
            }
        }
    
    }

除了使用MyBatis提供的DefaultReflectorFactory实现，我们还可以在mybatis-config.xml中配置自定义的ReflectorFactory实现类，从而实现功能上的扩展。

**TypeParameterResolver**

TypeParameterResolver是一个工具类，提供了一系列静态方法来解析指定类中的字段、方法返回值或方法参数的类型。

在开始介绍TypeParameterResolver之前，先简单介绍一下Type接口的基础知识。Type是所有类型的父接口，它有四个子接口和一个实现类，

![image][image 1]

**1、Class比较常见，它表示的是原始类型。**

Class类的对象表示JVM中的一个类或接口，每个Java类在JVM里都表现为一个Class对象。在程序中可以通过“类名.class”、“对象.getClass（）”或是“Class.forName（”类名”）”等方式获取Class对象。数组也被映射为Class 对象，所有元素类型相同且维数相同的数组都共享同一个 Class 对象。

2、**ParameterizedType表示的是参数化类型**

例如List＜String＞、Map＜Integer,String＞、Service＜User＞这种带有泛型的类型。

ParameterizedType接口中常用的方法有三个，分别是：

Type getRawType（）—返回参数化类型中的原始类型，例如List＜String＞的原始类型为List。 
    
    Type[] getActualTypeArguments（）—获取参数化类型的类型变量或是实际类型列表，例如Map＜Integer, String＞的实际泛型列表Integer和String。需要注意的是，该列表的元素类型都是Type，也就是说，可能存在多层嵌套的情况。 
    
    Type getOwnerType（）—返回是类型所属的类型，例如存在A＜T＞类，其中定义了内部类InnerA＜I＞，则InnerA＜I＞所属的类型为A＜T＞，如果是顶层类型则返回null。这种关系比较常见的示例是Map＜K,V＞接口与Map.Entry＜K,V＞接口，Map＜K,V＞接口是Map.Entry＜K,V＞接口的所有者。 · TypeVariable表示的是类型变量，它用来反映在JVM编译该泛型前的信息。例如List＜T＞中的T就是类型变量，它在编译时需被转换为一个具体的类型后才能正常使用。

TypeParameterResolver中各个静态方法之间的调用关系大致如图所示

![image][image 2]

TypeParameterResolver中通过resolveFieldType（）方法、resolveReturnType（）方法、resolveParamTypes（）方法分别解析字段类型、方法返回值类型和方法参数列表中各个参数的类型。具体实现可查看其源码及官方的单元测试方法。

**ObjectFactory接口**

MyBatis中有很多模块会使用到ObjectFactory接口，该接口提供了多个create（）方法的重载，通过这些create（）方法可以创建指定类型的对象。ObjectFactory接口的定义如下：

/** * Mybatis 使用ObjectFactory去创建需要的对象 * @author Clinton Begin */
    public interface ObjectFactory { 
    
        /** * 设置配置信息 * @param properties 配置信息 */
        void setProperties(Properties properties);
    
        /** * 通过默认构造函数创建指定类的对象 * @param type 对象类型 * @return */
        <T> T create(Class<T> type);
    
        /** * 根据参数列表，从指定类型中选择合适的构造器创建对象 * @param type 对象类型 * @param constructorArgTypes 参数类型 * @param constructorArgs 参数值 * @return */
        <T> T create(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs);
    
        /** * 检测指定类型是否是集合类型 * @param type 对象类型 * @return 集合类型返回true否则返回false * @since 3.1.0 */
        <T> boolean isCollection(Class<T> type);
    
    }

DefaultObjectFactory是MyBatis提供的ObjectFactory接口的唯一实现，它是一个反射工厂，其create（）方法通过调用instantiateClass（）方法实现。DefaultObjectFactory.instantiateClass（）方法会根据传入传入的参数列表选择合适的构造函数实例化对象，具体实现如下：

private  <T> T instantiateClass(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) { 
        try {
          Constructor<T> constructor;
          //通过无参构造函数创建对象
          if (constructorArgTypes == null || constructorArgs == null) {
            constructor = type.getDeclaredConstructor();
            if (!constructor.isAccessible()) {
              constructor.setAccessible(true);
            }
            return constructor.newInstance();
          }
          //根据参数列表查找合适的构造函数，并实例化对象
          constructor = type.getDeclaredConstructor(constructorArgTypes.toArray(new Class[constructorArgTypes.size()]));
          if (!constructor.isAccessible()) {
            constructor.setAccessible(true);
          }
          return constructor.newInstance(constructorArgs.toArray(new Object[constructorArgs.size()]));
        } catch (Exception e) {
          StringBuilder argTypes = new StringBuilder();
          if (constructorArgTypes != null && !constructorArgTypes.isEmpty()) {
            for (Class<?> argType : constructorArgTypes) {
              argTypes.append(argType.getSimpleName());
              argTypes.append(",");
            }
            argTypes.deleteCharAt(argTypes.length() - 1); // remove trailing ,
          }
          StringBuilder argValues = new StringBuilder();
          if (constructorArgs != null && !constructorArgs.isEmpty()) {
            for (Object argValue : constructorArgs) {
              argValues.append(String.valueOf(argValue));
              argValues.append(",");
            }
            argValues.deleteCharAt(argValues.length() - 1); // remove trailing ,
          }
          throw new ReflectionException("Error instantiating " + type + " with invalid types (" + argTypes + ") or values (" + argValues + "). Cause: " + e, e); } }

除了使用MyBatis提供的DefaultObjectFactory实现，我们还可以在mybatis-config.xml配置文件中指定自定义的ObjectFactory接口实现类，从而实现功能上的扩展。

[image]: http://om6hv2adi.bkt.clouddn.com/mybatis_DefaultReflectorFactory.png
[image 1]: http://om6hv2adi.bkt.clouddn.com/mybatis_type.png
[image 2]: http://om6hv2adi.bkt.clouddn.com/mybatis_TypeParameterResolver.png