mybatis-Executor插件

1. Interceptor 初始化创建 Configuration,解析配置的interceptor 添加到 interceptorChain

String resource = "com/sxteng/mybatis/XMLConfigBuilder/mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);

// 构建 SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

XMLConfigBuilder parse 生成 Configuration

解析配置信息

parseConfiguration(XNode root)

解析插件并添加到Configuration中

pluginElement(root.evalNode("plugins"));

// 解析插件并添加到环境当中                     
private void pluginElement(XNode parent) throws Exception {
    if (parent != null) {
      for (XNode child : parent.getChildren()) {
        String interceptor = child.getStringAttribute("interceptor");
        Properties properties = child.getChildrenAsProperties();
        Interceptor interceptorInstance = (Interceptor) 
        resolveClass(interceptor).newInstance();
        //设置配置属性
        interceptorInstance.setProperties(properties);
        //将插件添加的配置中
        configuration.addInterceptor(interceptorInstance);
      }
    }
  }

2. 为Executor 应用插件,生成代理对象

打开session

SqlSessionFactory .openSession()

  private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
    Transaction tx = null;
    try {
      final Environment environment = configuration.getEnvironment();
      final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
      tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
      final Executor executor = configuration.newExecutor(tx, execType);
      return new DefaultSqlSession(configuration, executor, autoCommit);
    } catch (Exception e) {
      closeTransaction(tx); // may have fetched a connection so lets call close()
      throw ExceptionFactory.wrapException("Error opening session.  Cause: " + e, e);
    } finally {
      ErrorContext.instance().reset();
    }
  }

创建Executor, 应用插件, 生成代理对象

Configuration..newExecutor(tx, execType);

  /**
     * 创建Executor
     * @param transaction
     * @param executorType
     * @return
     */
    public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
        executorType = executorType == null ? defaultExecutorType : executorType;
        executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
        Executor executor;
        if (ExecutorType.BATCH == executorType) {
            executor = new BatchExecutor(this, transaction);
        } else if (ExecutorType.REUSE == executorType) {
            executor = new ReuseExecutor(this, transaction);
        } else {
            // 事物
            executor = new SimpleExecutor(this, transaction);
        }
        //启动缓存
        if (cacheEnabled) {
            executor = new CachingExecutor(executor);
        }
        //应用插件
        executor = (Executor) interceptorChain.pluginAll(executor);
        return executor;
    }

遍历拦截器

  public Object pluginAll(Object target) {
    for (Interceptor interceptor : interceptors) {
      target = interceptor.plugin(target);
    }
    return target;
  }

3 Interceptor 的 plugin(Object target) 方法以PageHelper 为例

    public Object plugin(Object target) {
        if (target instanceof Executor) {
            return Plugin.wrap(target, this);
        } else {
            return target;
        }
    }

4 Plugin 的 wrap(Object target, Interceptor interceptor) 如何有接口则创建代理对象

  private Object target;  //目标对象
  private Interceptor interceptor;//拦截器
  private Map<Class<?>, Set<Method>> signatureMap;//方法签名

  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;
  }

InterceptorChain

Configuration XMLConfigBuilder.parse()

2 Configuration 重要属性

InterceptorChain 插件
proxyFactory

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