兄弟连区块链教程Fabric1.0源代码分析consenter（共识插件）#filter（过滤器），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 consenter（共识插件） #filter（过滤器）
## 1、filter概述
filter代码分布在orderer/common/filter、orderer/common/configtxfilter、orderer/common/sizefilter、orderer/common/sigfilter、orderer/multichain目录下。
orderer/common/filter/filter.go，Rule接口定义及emptyRejectRule和acceptRule实现，Committer接口定义及noopCommitter实现，RuleSet结构体及方法。
orderer/common/configtxfilter目录，configFilter结构体（实现Rule接口）及configCommitter结构体（实现Committer接口）。
orderer/common/sizefilter目录，maxBytesRule结构体（实现Rule接口）。
orderer/multichain/chainsupport.go，filter工具函数。
orderer/multichain/systemchain.go，systemChainFilter结构体（实现Rule接口）及systemChainCommitter结构体（实现Committer接口）。
## 2、Rule接口定义及实现
### 2.1、Rule接口定义
```go
type Action int
const (
Accept = iota
Reject
Forward
)
type Rule interface { //定义一个过滤器函数, 它接受、拒绝或转发 (到下一条规则) 一个信封
Apply(message *ab.Envelope) (Action, Committer)
}
//代码在orderer/common/filter/filter.go
```
### 2.2、emptyRejectRule（校验是否为空过滤器）
```go
type emptyRejectRule struct{}
var EmptyRejectRule = Rule(emptyRejectRule{})
func (a emptyRejectRule) Apply(message *ab.Envelope) (Action, Committer) {
if message.Payload == nil {
return Reject, nil
}
return Forward, nil
}
//代码在orderer/common/filter/filter.go
```
### 2.3、acceptRule（接受过滤器）
```go
type acceptRule struct{}
var AcceptRule = Rule(acceptRule{})
func (a acceptRule) Apply(message *ab.Envelope) (Action, Committer) {
return Accept, NoopCommitter
}
//代码在orderer/common/filter/filter.go
```
### 2.4、configFilter（配置交易合法性过滤器）
```go
type configFilter struct {
configManager api.Manager
}
func NewFilter(manager api.Manager) filter.Rule //构造configFilter
//配置交易过滤器
func (cf *configFilter) Apply(message *cb.Envelope) (filter.Action, filter.Committer) {
msgData, err := utils.UnmarshalPayload(message.Payload) //获取Payload
chdr, err := utils.UnmarshalChannelHeader(msgData.Header.ChannelHeader) //获取ChannelHeader
if chdr.Type != int32(cb.HeaderType_CONFIG) { //配置交易
return filter.Forward, nil
}
configEnvelope, err := configtx.UnmarshalConfigEnvelope(msgData.Data) //获取configEnvelope
err = cf.configManager.Validate(configEnvelope) //校验configEnvelope
return filter.Accept, &configCommitter{
manager: cf.configManager,
configEnvelope: configEnvelope,
}
}
//代码在orderer/common/configtxfilter/filter.go
```
### 2.5、sizefilter（交易大小过滤器）
```go
type maxBytesRule struct {
support Support
}
func MaxBytesRule(support Support) filter.Rule //构造maxBytesRule
func (r *maxBytesRule) Apply(message *cb.Envelope) (filter.Action, filter.Committer) {
maxBytes := r.support.BatchSize().AbsoluteMaxBytes
if size := messageByteSize(message); size > maxBytes {
return filter.Reject, nil
}
return filter.Forward, nil
}
//代码在orderer/common/sizefilter/sizefilter.go
```
### 2.6、sigFilter（签名数据校验过滤器）
```go
type sigFilter struct {
policySource string
policyManager policies.Manager
}
func New(policySource string, policyManager policies.Manager) filter.Rule //构造sigFilter
func (sf *sigFilter) Apply(message *cb.Envelope) (filter.Action, filter.Committer) {
signedData, err := message.AsSignedData() //构造SignedData
policy, ok := sf.policyManager.GetPolicy(sf.policySource) //获取策略
err = policy.Evaluate(signedData) //校验策略
if err == nil {
return filter.Forward, nil
}
return filter.Reject, nil
}
//代码在orderer/common/sigfilter/sigfilter.go
```