TestMapper testMapper = session.getMapper(TestMapper.class);
Test test = testMapper.findOne(1);

public T newInstance(SqlSession sqlSession) {
    // mapperProxy 實(shí)現(xiàn)了 InvocationHandler 接口，用于 JDK 動(dòng)態(tài)代理
    final MapperProxy<T> mapperProxy = new MapperProxy<>(sqlSession, mapperInterface, methodCache);
    return newInstance(mapperProxy);
}
// 通過(guò) JDK 動(dòng)態(tài)代理生成對(duì)象
protected T newInstance(MapperProxy<T> mapperProxy) {
    return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), 
        new Class[]{ mapperInterface }, mapperProxy);
}

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());
    }
    // ...
    return result;
}

public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds,
                        ResultHandler resultHandler, CacheKey key, BoundSql boundSql)
    throws SQLException {
    Cache cache = ms.getCache();
    if (cache != null) {
        flushCacheIfRequired(ms);
        if (ms.isUseCache() && resultHandler == null) {
            ensureNoOutParams(ms, boundSql);
            @SuppressWarnings("unchecked")
            List<E> list = (List<E>) tcm.getObject(cache, key);
            if (list == null) {
                list = delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
                // 放緩存
                tcm.putObject(cache, key, list); // issue #578 and #116
            }
            return list;
        }
    }
    // 若二級(jí)緩存為空，則重新查詢數(shù)據(jù)庫(kù)
    return delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}

private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
    Statement stmt;
    Connection connection = getConnection(statementLog);
    stmt = handler.prepare(connection, transaction.getTimeout());
    handler.parameterize(stmt);
    return stmt;
}

SimpleStatementHandler
public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
    String sql = boundSql.getSql();
    statement.execute(sql);
    return resultSetHandler.<E>handleResultSets(statement);
}