聊聊mybatis的Interceptor机制

最新推荐文章于 2025-08-14 17:26:49 发布

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最新推荐文章于 2025-08-14 17:26:49 发布 · 516 阅读

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文章标签：

#mybatis

本文详细解析了MyBatis中的Interceptor接口及其工作原理，包括Invocation、Plugin的包装与调用，以及如何在Spring集成中通过XML配置和自动配置类注册Interceptor，实现对SQL执行过程的拦截。

序

本文主要研究一下mybatis的Interceptor机制

Interceptor

org/apache/ibatis/plugin/Interceptor.java

public interface Interceptor {

  Object intercept(Invocation invocation) throws Throwable;

  default Object plugin(Object target) {
    return Plugin.wrap(target, this);
  }

  default void setProperties(Properties properties) {
    // NOP
  }

}

Interceptor定义了intercept方法，其参数为Invocation类型，同时默认提供了plugin方法，通过Plugin.wrap(target, this)进行包装

Invocation

org/apache/ibatis/plugin/Invocation.java

public class Invocation {

  private final Object target;
  private final Method method;
  private final Object[] args;

  public Invocation(Object target, Method method, Object[] args) {
    this.target = target;
    this.method = method;
    this.args = args;
  }

  public Object getTarget() {
    return target;
  }

  public Method getMethod() {
    return method;
  }

  public Object[] getArgs() {
    return args;
  }

  public Object proceed() throws InvocationTargetException, IllegalAccessException {
    return method.invoke(target, args);
  }

}

Invocation定义了target、method、args属性，提供了proceed方法则是反射执行method方法

Plugin

org/apache/ibatis/plugin/Plugin.java

public class Plugin implements InvocationHandler {

  private final Object target;
  private final Interceptor interceptor;
  private final Map<Class<?>, Set<Method>> signatureMap;

  private Plugin(Object target, Interceptor interceptor, Map<Class<?>, Set<Method>> signatureMap) {
    this.target = target;
    this.interceptor = interceptor;
    this.signatureMap = signatureMap;
  }

  public static Object wrap(Object target, Interceptor interceptor) {
    Map<Class<?>, Set<Method>> signatureMap = getSignatureMap(interceptor);
    Class<?> type = target.getClass();
    Class<?>[] interfaces = getAllInterfaces(type, signatureMap);
    if (interfaces.length > 0) {
      return Proxy.newProxyInstance(type.getClassLoader(), interfaces, new Plugin(target, interceptor, signatureMap));
    }
    return target;
  }

  @Override
  public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    try {
      Set<Method> methods = signatureMap.get(method.getDeclaringClass());
      if (methods != null && methods.contains(method)) {
        return interceptor.intercept(new Invocation(target, method, args));
      }
      return method.invoke(target, args);
    } catc