缘起

最近阅读 [Offer来了：Java面试核心知识点精讲（框架篇）] (王磊 , 2020.6)
本系列笔记拟采用golang练习之
Talk is cheap, show me the code.

Spring

Spring基于J2EE技术实现了一套轻量级的
Java Web Service系统应用框架。
它有很多优秀的特性，很多公司都选择把
Spring作为产品或项目的基础开发架构。
Spring的特性包括轻量、控制反转
（Inversion of Control, IoC）、
面向容器、面向切面（AspectOriented 
Programming, AOP）和框架灵活等。
源码gitee地址：
https://gitee.com/ioly/learning.gooop
原文链接：
https://my.oschina.net/ioly

目标

• 参考spring常用注解，使用golang编写“基于注解的静态代码增强器/生成器”
  • 配置： ComponentScan，Configuration, Bean
  • Bean声明：Component, Service, Controller
  • Bean注入：Autowried
    
  • AOP注解：Before, After, Around, PointCut

子目标（Day 2）

• 构思app的运行模式：
  • 本地standlone模式运行
  • 提供基于cli的命令行实时交互
  • 生成旁路代码：只扫描源代码，不修改源代码，增强后的代码加统一后缀
• 设计cli交互指令集：
  • config save：保存配置
  • config saveas ：另存配置
  • watch add ：添加代码扫描目录
  • watch del ：移除代码扫描目录
  • watch list：显示当前扫描的代码目录集合
  • gen：生成增强代码，也就是扫描所有注解，并生成增强类和增强方法

设计

• config/IConfiguration：配置接口
• command/ICmd：指令接口
• command/ICmdBuilder：指令构建器接口
• command/ICmdContext：指令执行上下文接口
• config_cmd/SaveCmd: 保存配置
• config_cmd/SaveASCmd: 另存配置
• watch_cmd/AddCmd: 添加监视
• watch_cmd/DelCmd: 移除监视
• watch_cmd/ListCmd: 显示已监视目录的列表
• gen_cmd/GenCmd: 生成增强类和增强方法
• model/IEventDrivenModel：“事件驱动”的逻辑编排模型
• logger: 日志接口，略

config/IConfiguration.go

配置接口

package config
// IConfiguration defines system configuration interface
type IConfiguration interface {
    GetProjectName() string
    SetProjectName(string)
    GetWatchPaths() []string
    AddWatchPath(string)
    DelWatchPath(string)
    Save() error
    SaveAS(string) error
}

command/ICmd.go

指令接口

package command
import "fmt"
// ICmd defines cli command interface
type ICmd interface {
    fmt.Stringer
    // Apply apply current command into use
    Apply(ICmdContext) error
}

command/ICmdBuilder.go

指令构建器接口

package command
// ICmdBuilder parse input string and create an ICmd instance
type ICmdBuilder interface {
    Build(string) (error, ICmd)
}

command/ICmdContext.go

指令执行上下文接口

package command
import "learning/gooop/spring/autogen/config"
// ICmdContext provides context info for all commands
type ICmdContext interface {
    GetConfiguration() config.IConfiguration
}

config_cmd/SaveCmd.go

保存配置

package config_cmd
import (
    "learning/gooop/spring/autogen/command"
)
// SaveCmd calls service.Save() to save current configuration, in JSON format
type SaveCmd int
// SaveCmdBuilder parse cli input and build a SaveCmd instance
type SaveCmdBuilder int
const gSaveCmdString = "config save"
var gSaveCmdInstance = new(SaveCmd)
func (me *SaveCmd) String() string {
    return gSaveCmdString
}
func (me *SaveCmd) Apply(c command.ICmdContext) error {
    // todo: fixme
    panic("implements me")
}
func (me *SaveCmdBuilder) Build(line string) (error, command.ICmd) {
    if line != gSaveCmdString {
        return nil, nil
    }
    return nil, gSaveCmdInstance
}

config_cmd/SaveASCmd.go

另存配置

package config_cmd
import (
    "errors"
    "learning/gooop/spring/autogen/command"
    "strings"
)
// SaveASCmd calls service.SaveAS() to save current config into specific file, in JSON format
type SaveASCmd struct {
    file string
}
// SaveASCmdBuilder parse cli input and returns a SaveASCmd instance
type SaveASCmdBuilder int
const gSaveASCmdPrefix = "config saveas "
func (me *SaveASCmd) String() string {
    return gSaveASCmdPrefix + me.file
}
func (me *SaveASCmd) Apply(c command.ICmdContext) error {
    // todo: fixme
    panic("implements me")
}
func (me *SaveASCmdBuilder) Build(line string) (error, command.ICmd) {
    if !strings.HasPrefix(line, gSaveASCmdPrefix) {
        return nil, nil
    }
    file := strings.TrimSpace(line[len(gSaveASCmdPrefix):])
    if len(file) <= 0 {
        return errors.New("empty file path"), nil
    }
    return nil, &SaveASCmd{file }
}

watch_cmd/AddCmd.go

添加监视

package watch_cmd
import (
    "learning/gooop/spring/autogen/command"
    "os"
    "strings"
)
// AddCmd calls service.WatchAdd() to add dir to watch list
type AddCmd struct {
    dir string
}
type AddCmdBuilder int
var gAddCmdPrefix = "watch add "
func (me *AddCmd) String() string {
    return gAddCmdPrefix + me.dir
}
func (me *AddCmd) Apply(c command.ICmdContext) error {
    // todo: fixme
    panic("implements me")
}
func (me *AddCmdBuilder) Build(line string) (error, command.ICmd) {
    // check prefix
    if !strings.HasPrefix(line, gAddCmdPrefix) {
        return nil, nil
    }
    // get dir
    dir := strings.TrimSpace(line[len(gAddCmdPrefix):])
    // check dir
    _,e := os.Stat(dir)
    if e != nil {
        return e, nil
    }
    // ok
    return nil, &AddCmd{dir }
}

watch_cmd/DelCmd.go

移除监视

package watch_cmd
import (
    "learning/gooop/spring/autogen/command"
    "os"
    "strings"
)
// DelCmd calls service.WatchDel() to remove dir from watch list
type DelCmd struct {
    dir string
}
type DelCmdBuilder int
var gDelCmdPrefix = "watch del "
func (me *DelCmd) String() string {
    return gDelCmdPrefix + me.dir
}
func (me *DelCmd) Apply(c command.ICmdContext) error {
    // todo: fixme
    panic("implements me")
}
func (me *DelCmdBuilder) Build(line string) (error, command.ICmd) {
    // check prefix
    if !strings.HasPrefix(line, gDelCmdPrefix) {
        return nil, nil
    }
    // get dir
    dir := strings.TrimSpace(line[len(gAddCmdPrefix):])
    // check dir
    _,e := os.Stat(dir)
    if e != nil {
        return e, nil
    }
    // ok
    return nil, &DelCmd{ dir }
}

watch_cmd/ListCmd.go

显示已监视目录的列表

package watch_cmd
import (
    "learning/gooop/spring/autogen/command"
)
// ListCmd calls service.WatchList
type ListCmd int
// ListCmdBuilder parse cli input and try to build a ListCmd instance
type ListCmdBuilder int
const gListCmdString1 = "watch list"
const gListCmdString2 = "watch ls"
var gListCmdSingleton = new(ListCmd)
func (me *ListCmd) String() string {
    return gListCmdString1
}
func (me *ListCmd) Apply(c command.ICmdContext) error {
    // todo:
    panic("implements me")
}
func (me *ListCmdBuilder) Build(line string) (error, command.ICmd) {
    if line != gListCmdString1 && line != gListCmdString2 {
        return nil, nil
    }
    return nil, gListCmdSingleton
}

gen_cmd/GenCmd.go

生成增强类和增强方法

package gen_cmd
import (
    "learning/gooop/spring/autogen/command"
)
// GenCmd calls service.Gen() to generate enhanced code files at once
type GenCmd int
// GenCmdBuilder parse cli input and try to build a GenCmd instance
type GenCmdBuilder int
const gGenCmdString = "gen"
var gGenCmdSingleton = new(GenCmd)
func (me *GenCmd) String() string {
    return gGenCmdString
}
func (me *GenCmd) Apply(c command.ICmdContext) error {
    panic("implements me")
}
func (me *GenCmdBuilder) Build(line string) (error, command.ICmd) {
    if line != gGenCmdString {
        return nil, nil
    }
    return nil, gGenCmdSingleton
}

model/IEventDrivenModel.go

“事件驱动”的逻辑编排模型

package model
// IEventDrivenModel defines an event driven model for code arrangement
type IEventDrivenModel interface {
    Hook(e string, handleFunc TEventHandleFunc)
    Fire(e string, args ...interface{})
    FireAsync(e string, args ...interface{})
}
type TEventHandleFunc func(e string, args ...interface{})
type TEventDrivenModel struct {
    items map[string][]TEventHandleFunc
}
func (me *TEventDrivenModel) Hook(e string, handler TEventHandleFunc) {
    if me.items == nil {
        me.items = make(map[string][]TEventHandleFunc)
    }
    arr, ok := me.items[e]
    if ok {
        me.items[e] = append(arr, handler)
    } else {
        me.items[e] = []TEventHandleFunc{handler}
    }
}
func (me *TEventDrivenModel) Fire(e string, args ...interface{}) {
    if handlers, ok := me.items[e]; ok {
        for _, it := range handlers {
            it(e, args...)
        }
    }
}
func (me *TEventDrivenModel) FireAsync(e string, args ...interface{}) {
    go me.Fire(e, args...)
}

（未完待续）