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  兄弟连区块链教程Fabric1.0源代码分析policy(背书策略),2018年下半年,区块链行业正逐渐褪去发展之初的浮躁、回归理性,表面上看相关人才需求与身价似乎正在回落。但事实上,正是初期泡沫的渐退,让人们更多的关注点放在了区块链真正的技术之上。
# Fabric 1.0源代码笔记 之 policy(背书策略)
## 1、policy概述
policy代码分布在core/policy、core/policyprovider、common/policies目录下。目录结构如下:
* core/policy/policy.go,PolicyChecker接口定义及实现、PolicyCheckerFactory接口定义。
* core/policyprovider/provider.go,PolicyChecker工厂默认实现。
* common/policies目录
    * policy.go,ChannelPolicyManagerGetter接口及实现。
    * implicitmeta_util.go,通道策略工具函数。
## 2、PolicyChecker工厂
### 2.1、PolicyCheckerFactory接口定义
```go
type PolicyCheckerFactory interface {
    NewPolicyChecker() PolicyChecker //构造PolicyChecker实例
}
var pcFactory PolicyCheckerFactory //全局变量定义及赋值函数
func RegisterPolicyCheckerFactory(f PolicyCheckerFactory) {
    pcFactory = f
}
//代码在core/policy/policy.go
```
### 2.2、PolicyCheckerFactory接口默认实现
```go
type defaultFactory struct{}
//构造policy.PolicyChecker
func (f *defaultFactory) NewPolicyChecker() policy.PolicyChecker {
    return policy.NewPolicyChecker(
        peer.NewChannelPolicyManagerGetter(), //&channelPolicyManagerGetter{}
        mgmt.GetLocalMSP(),
        mgmt.NewLocalMSPPrincipalGetter(),
    )
}
//获取policy.PolicyChecker,即调用policy.GetPolicyChecker()
func GetPolicyChecker() policy.PolicyChecker
func init() { //初始化全局变量pcFactory
    policy.RegisterPolicyCheckerFactory(&defaultFactory{})
}
```
## 3、PolicyChecker接口定义及实现
### 3.1、PolicyChecker接口定义
```go
type PolicyChecker interface {
    CheckPolicy(channelID, policyName string, signedProp *pb.SignedProposal) error
    CheckPolicyBySignedData(channelID, policyName string, sd []*common.SignedData) error
    CheckPolicyNoChannel(policyName string, signedProp *pb.SignedProposal) error
}
//代码在core/policy/policy.go
```
### 3.2、PolicyChecker接口实现
PolicyChecker接口实现,即policyChecker结构体及方法。
```go
type policyChecker struct {
    channelPolicyManagerGetter policies.ChannelPolicyManagerGetter //通道策略管理器
    localMSP                   msp.IdentityDeserializer //身份
    principalGetter            mgmt.MSPPrincipalGetter //委托人
}
//构造policyChecker
func NewPolicyChecker(channelPolicyManagerGetter policies.ChannelPolicyManagerGetter, localMSP msp.IdentityDeserializer, principalGetter mgmt.MSPPrincipalGetter) PolicyChecker
//检查签名提案是否符合通道策略
func (p *policyChecker) CheckPolicy(channelID, policyName string, signedProp *pb.SignedProposal) error
func (p *policyChecker) CheckPolicyNoChannel(policyName string, signedProp *pb.SignedProposal) error
//检查签名数据是否符合通道策略,获取策略并调取policy.Evaluate(sd)
func (p *policyChecker) CheckPolicyBySignedData(channelID, policyName string, sd []*common.SignedData) error
func GetPolicyChecker() PolicyChecker //pcFactory.NewPolicyChecker()
//代码在core/policy/policy.go
```
func (p *policyChecker) CheckPolicy(channelID, policyName string, signedProp *pb.SignedProposal) error代码如下:
```go
func (p *policyChecker) CheckPolicy(channelID, policyName string, signedProp *pb.SignedProposal) error {
    if channelID == "" { //channelID为空,调取CheckPolicyNoChannel()
        return p.CheckPolicyNoChannel(policyName, signedProp)
    }
   
    policyManager, _ := p.channelPolicyManagerGetter.Manager(channelID)
    proposal, err := utils.GetProposal(signedProp.ProposalBytes) //获取proposal
    header, err := utils.GetHeader(proposal.Header)
    shdr, err := utils.GetSignatureHeader(header.SignatureHeader) //SignatureHeader
    sd := []*common.SignedData{&common.SignedData{
        Data:      signedProp.ProposalBytes,
        Identity:  shdr.Creator,
        Signature: signedProp.Signature,
    }}
    return p.CheckPolicyBySignedData(channelID, policyName, sd)
}
//代码在core/policy/policy.go
```
## 4、ChannelPolicyManagerGetter接口及实现
### 4.1、ChannelPolicyManagerGetter接口定义
```go
type ChannelPolicyManagerGetter interface {
    Manager(channelID string) (Manager, bool)
}
//代码在common/policies/policy.go
```
### 4.2、ChannelPolicyManagerGetter接口实现
ChannelPolicyManagerGetter接口实现,即ManagerImpl结构体及方法。
```go
type ManagerImpl struct {
    parent        *ManagerImpl
    basePath      string
    fqPrefix      string
    providers     map[int32]Provider //type Provider interface
    config        *policyConfig //type policyConfig struct
    pendingConfig map[interface{}]*policyConfig //type policyConfig struct
    pendingLock   sync.RWMutex
    SuppressSanityLogMessages bool
}
type Provider interface {
    NewPolicy(data []byte) (Policy, proto.Message, error)
}
type policyConfig struct {
    policies map[string]Policy //type Policy interface
    managers map[string]*ManagerImpl
    imps     []*implicitMetaPolicy
}
type Policy interface {
    //对给定的签名数据,按规则检验确认是否符合约定的条件
    Evaluate(signatureSet []*cb.SignedData) error
}
//构造ManagerImpl
func NewManagerImpl(basePath string, providers map[int32]Provider) *ManagerImpl
//获取pm.basePath
func (pm *ManagerImpl) BasePath() string
//获取pm.config.policies,即map[string]Policy中Key列表
func (pm *ManagerImpl) PolicyNames() []string
//获取指定路径的子管理器
func (pm *ManagerImpl) Manager(path []string) (Manager, bool)
//获取pm.config.policies[relpath]
//获取Policy
func (pm *ManagerImpl) GetPolicy(id string) (Policy, bool)
func (pm *ManagerImpl) BeginPolicyProposals(tx interface{}, groups []string) ([]Proposer, error)
func (pm *ManagerImpl) RollbackProposals(tx interface{})
func (pm *ManagerImpl) PreCommit(tx interface{}) error
func (pm *ManagerImpl) CommitProposals(tx interface{})
func (pm *ManagerImpl) ProposePolicy(tx interface{}, key string, configPolicy *cb.ConfigPolicy) (proto.Message, error)
//代码在common/policies/policy.go
```
```go
type implicitMetaPolicy struct {
    conf        *cb.ImplicitMetaPolicy
    threshold   int
    subPolicies []Policy
}
//代码在common/policies/implicitmeta.go
```
## 5、通道策略工具函数
```go
type ImplicitMetaPolicy_Rule int32
const (
    ImplicitMetaPolicy_ANY      ImplicitMetaPolicy_Rule = 0 //任意
    ImplicitMetaPolicy_ALL      ImplicitMetaPolicy_Rule = 1 //所有
    ImplicitMetaPolicy_MAJORITY ImplicitMetaPolicy_Rule = 2 //大多数
)
//代码在protos/common/policies.pb.go
```
```go
//构造cb.Policy
func ImplicitMetaPolicyWithSubPolicy(subPolicyName string, rule cb.ImplicitMetaPolicy_Rule) *cb.ConfigPolicy
func TemplateImplicitMetaPolicyWithSubPolicy(path []string, policyName string, subPolicyName string, rule cb.ImplicitMetaPolicy_Rule) *cb.ConfigGroup
//调取TemplateImplicitMetaPolicyWithSubPolicy(path, policyName, policyName, rule)
func TemplateImplicitMetaPolicy(path []string, policyName string, rule cb.ImplicitMetaPolicy_Rule) *cb.ConfigGroup
//任意,TemplateImplicitMetaPolicy(path, policyName, cb.ImplicitMetaPolicy_ANY)
func TemplateImplicitMetaAnyPolicy(path []string, policyName string) *cb.ConfigGroup
//所有,TemplateImplicitMetaPolicy(path, policyName, cb.ImplicitMetaPolicy_ALL)
func TemplateImplicitMetaAllPolicy(path []string, policyName string) *cb.ConfigGroup
//大多数,TemplateImplicitMetaPolicy(path, policyName, cb.ImplicitMetaPolicy_MAJORITY)
func TemplateImplicitMetaMajorityPolicy(path []string, policyName string) *cb.ConfigGroup
//代码在common/policies/implicitmeta_util.go
```
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