mybatis-反射-reflection

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目录

概 述

mybatis提供反射包提炼、封装、增强反射api:
factory 包提供了对象工厂的缺省实现。
在缺省的实现：

 private  <T> T instantiateClass(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
    try {
      Constructor<T> constructor;
      if (constructorArgTypes == null || constructorArgs == null) {
        constructor = type.getDeclaredConstructor();
        try {
          return constructor.newInstance();
        } catch (IllegalAccessException e) {
          if (Reflector.canControlMemberAccessible()) {
            constructor.setAccessible(true);
            return constructor.newInstance();
          } else {
            throw e;
          }
        }
      }
      constructor = type.getDeclaredConstructor(constructorArgTypes.toArray(new Class[0]));
      try {
        return constructor.newInstance(constructorArgs.toArray(new Object[0]));
      } catch (IllegalAccessException e) {
        if (Reflector.canControlMemberAccessible()) {
          constructor.setAccessible(true);
          return constructor.newInstance(constructorArgs.toArray(new Object[0]));
        } else {
          throw e;
        }
      }
    } catch (Exception e) {
      String argTypes = Optional.ofNullable(constructorArgTypes).orElseGet(Collections::emptyList)
          .stream().map(Class::getSimpleName).collect(Collectors.joining(","));
      String argValues = Optional.ofNullable(constructorArgs).orElseGet(Collections::emptyList)
          .stream().map(String::valueOf).collect(Collectors.joining(","));
      throw new ReflectionException("Error instantiating " + type + " with invalid types (" + argTypes + ") or values (" + argValues + "). Cause: " + e, e);
    }
  }

Invoker定义:

public interface Invoker {
  Object invoke(Object target, Object[] args) throws IllegalAccessException, InvocationTargetException;

  Class<?> getType();
}

主要是把Field给抽象出来。
property
核心的是将：

public class PropertyTokenizer implements Iterator<PropertyTokenizer> {
  private String name;
  private final String indexedName;
  private String index;
  private final String children;

  public PropertyTokenizer(String fullname) {
    int delim = fullname.indexOf('.');
    if (delim > -1) {
      name = fullname.substring(0, delim);
      children = fullname.substring(delim + 1);
    } else {
      name = fullname;
      children = null;
    }
    indexedName = name;
    delim = name.indexOf('[');
    if (delim > -1) {
      index = name.substring(delim + 1, name.length() - 1);
      name = name.substring(0, delim);
    }
  }

wapper包，
放着ObjectWapper及其实现类。

 Object get(PropertyTokenizer prop);

  void set(PropertyTokenizer prop, Object value);

  String findProperty(String name, boolean useCamelCaseMapping);

  String[] getGetterNames();

  String[] getSetterNames();

  Class<?> getSetterType(String name);

  Class<?> getGetterType(String name);

  boolean hasSetter(String name);

  boolean hasGetter(String name);

  MetaObject instantiatePropertyValue(String name, PropertyTokenizer prop, ObjectFactory objectFactory);

  boolean isCollection();

  void add(Object element);

  <E> void addAll(List<E> element);

BaseWrapper

ReflectorFactory
Reflector工厂，就是控制Reflector的创建，目的是为了缓存Reflector，

 static class Section extends AbstractEntity implements Entity<Long> {
  }

测试代码：

```java
 interface Entity<T> {
    T getId();

    void setId(T id);
  }

  static abstract class AbstractEntity implements Entity<Long> {

    private Long id;

    @Override
    public Long getId() {
      return id;
    }

    @Override
    public void setId(Long id) {
      this.id = id;
    }
  }

 static class Section extends AbstractEntity implements Entity<Long> {
  }

同样我们也可以对对应的setting类型进行判断：

 @Test
  void shouldResolveArraySetterParam() {
    ReflectorFactory reflectorFactory = new DefaultReflectorFactory();
    Reflector reflector = reflectorFactory.findForClass(Child.class);
    Class<?> clazz = reflector.getSetterType("array");
    assertTrue(clazz.isArray());
    assertEquals(String.class, clazz.getComponentType());
  }

```java
  @Test
  void testGetSetterType() {
    ReflectorFactory reflectorFactory = new DefaultReflectorFactory();
    Reflector reflector = reflectorFactory.findForClass(Section.class);
    Assertions.assertEquals(Long.class, reflector.getSetterType("id"));
  }

‘’

小结

参考资料和推荐阅读

1.链接: link

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