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MapperMethod与MapperProxy,MapperProxyFactory,MapperRegistry,Configuration之间的关系

在分析mapper动态代理的时候可以看出最终执行的是mapperMethod.execute

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {    try {      //当执行的方法是继承自Object时执行this里的相应方法      if (Object.class.equals(method.getDeclaringClass())) {        return method.invoke(this, args);      } else if (isDefaultMethod(method)) {        return invokeDefaultMethod(proxy, method, args);      }    } catch (Throwable t) {      throw ExceptionUtil.unwrapThrowable(t);    }    //最终执行的是mapperMethod.execute    final MapperMethod mapperMethod = cachedMapperMethod(method);    return mapperMethod.execute(sqlSession, args);  }

接着分析mapperMethod.execute()

首先看MapperProxy中cachedMapperMethod(method)

/** * methodCache中已经存在传入的参数method * 则从methodCache中取MapperMethod, * 否则根据method生成MapperMethod实例并存储到methodCache中 * * @param method * @return */  private MapperMethod cachedMapperMethod(Method method) {    MapperMethod mapperMethod = methodCache.get(method);    if (mapperMethod == null) {      mapperMethod = new MapperMethod(mapperInterface, method, sqlSession.getConfiguration());      methodCache.put(method, mapperMethod);    }    return mapperMethod;  }

MapperProxy中methodCache

private final Map
    
      methodCache;
    

追溯methodCache的来源

//MapperProxy构造方法  public MapperProxy(SqlSession sqlSession, Class
    
      mapperInterface, Map
     
       methodCache) {    this.sqlSession = sqlSession;    this.mapperInterface = mapperInterface;    this.methodCache = methodCache;  }
     
    

MapperProxyFactory中

private final Map
    
      methodCache = new ConcurrentHashMap
     
      ();  public T newInstance(SqlSession sqlSession) {    final MapperProxy
      
        mapperProxy = new MapperProxy
       
        (sqlSession, mapperInterface, methodCache);    return newInstance(mapperProxy);  }
       
      
     
    

从MapperProxyFactory的源码中可以看出methodCache最初是一个空的ConcurrentHashMap,

从MapperProxy中cachedMapperMethod(method)可以看出

 methodCache中已经存在传入的参数method, 则从methodCache中取MapperMethod, 否则根据method生成MapperMethod实例并存储到methodCache中.

接着看MapperMethod的源码

构造方法

/**   * @param mapperInterface 接口   * @param method 调用的方法   * @param config 配置   */  public MapperMethod(Class
     mapperInterface, Method method, Configuration config) {    this.command = new SqlCommand(config, mapperInterface, method);    this.method = new MethodSignature(config, mapperInterface, method);  }

创建了SqlCommand和MethodSignature实例

command type

public enum SqlCommandType {  UNKNOWN, INSERT, UPDATE, DELETE, SELECT, FLUSH;}

MapperMethod中最重要的方法

public Object execute(SqlSession sqlSession, Object[] args) {    Object result;    switch (command.getType()) {      case INSERT: {    	Object param = method.convertArgsToSqlCommandParam(args);        result = rowCountResult(sqlSession.insert(command.getName(), param));        break;      }      case UPDATE: {        Object param = method.convertArgsToSqlCommandParam(args);        result = rowCountResult(sqlSession.update(command.getName(), param));        break;      }      case DELETE: {        Object param = method.convertArgsToSqlCommandParam(args);        result = rowCountResult(sqlSession.delete(command.getName(), param));        break;      }      case SELECT:        if (method.returnsVoid() && method.hasResultHandler()) {          executeWithResultHandler(sqlSession, args);          result = null;        } else if (method.returnsMany()) {          result = executeForMany(sqlSession, args);        } else if (method.returnsMap()) {          result = executeForMap(sqlSession, args);        } else if (method.returnsCursor()) {          result = executeForCursor(sqlSession, args);        } else {          Object param = method.convertArgsToSqlCommandParam(args);          result = sqlSession.selectOne(command.getName(), param);        }        break;      case FLUSH:        result = sqlSession.flushStatements();        break;      default:        throw new BindingException("Unknown execution method for: " + command.getName());    }    if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {      throw new BindingException("Mapper method '" + command.getName()           + " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");    }    return result;  }

首先调用MethodSignature里的

public Object convertArgsToSqlCommandParam(Object[] args)

处理参数.然后,

如果command type是

INSERT, UPDATE, DELETE

则直接调用sqlSession的相应方法

如果command type是

SELECT

则根据返回结果调用sqlSession里相应的查询方法.

至此MapperMethod从创建到执行的过程都大致分析了一遍.