chaincode的开发一般是使用GO或者JAVA，由于超级账本本身就是由go语言编写的，因此一般选用GO语言。ChainCode代码需要定义一个结构体struct，然后在该struct上实现ChainCode定义Init和Invoke两个函数。main函数作为ChainCode的启动入口。Init和Invoke方法是其两个重要的方法。应用程序请求运行智能合约fabcar后，Invoke方法被调用。在Invoke的时候，由传入的参数来决定我们具体调用了哪个方法，所以需要用GetFunctionAndParameters解析调用的时候传入的参数。
首先给出如下的示例：
type Foo struct {
}
func (this *Foo) Init(stub shim.ChaincodeStubInterface) peer.Response {
return shim.Success(nil)
}
func (this *Foo) Invoke(stub shim.ChaincodeStubInterface) peer.Response {
return shim.Success(nil)
}
在Init和Invoke方法中都会传入参数stub shim.ChaincodeStubInterface，这个参数提供的接口为我们编写ChainCode的业务逻辑提供了大量实用的方法。
获得调用的函数
GetArgs() [][]byte 以byte数组的数组的形式获得传入的参数列表
GetStringArgs() []string 以字符串数组的形式获得传入的参数列表
GetFunctionAndParameters() (string, []string) 将字符串数组的参数分为两部分，数组第一个字是Function，剩下的都是Parameter
GetArgsSlice() ([]byte, error) 以byte切片的形式获得参数列表
增删改查State DB
ChainCode核心的操作就是对State Database的增删改查，对此Fabric接口提供了3个对State DB的操作方法。
增改数据PutState(key string, value []byte) error
删除数据DelState(key string) error
查询数据GetState(key string) ([]byte, error)
ChaincodeStubInterface 定义如下所示：
type ChaincodeStubInterface interface {
// GetArgs returns the arguments intended for the chaincode Init and Invoke
// as an array of byte arrays.
GetArgs() [][]byte
// GetStringArgs returns the arguments intended for the chaincode Init and
// Invoke as a string array. Only use GetStringArgs if the client passes
// arguments intended to be used as strings.
GetStringArgs() []string
// GetFunctionAndParameters returns the first argument as the function
// name and the rest of the arguments as parameters in a string array.
// Only use GetFunctionAndParameters if the client passes arguments intended
// to be used as strings.
GetFunctionAndParameters() (string, []string)
// GetArgsSlice returns the arguments intended for the chaincode Init and
// Invoke as a byte array
GetArgsSlice() ([]byte, error)
// GetTxID returns the tx_id of the transaction proposal, which is unique per
// transaction and per client. See ChannelHeader in protos/common/common.proto
// for further details.
GetTxID() string
// GetChannelID returns the channel the proposal is sent to for chaincode to process.
// This would be the channel_id of the transaction proposal (see ChannelHeader
// in protos/common/common.proto) except where the chaincode is calling another on
// a different channel
GetChannelID() string
// InvokeChaincode locally calls the specified chaincode `Invoke` using the
// same transaction context; that is, chaincode calling chaincode doesn't
// create a new transaction message.
// If the called chaincode is on the same channel, it simply adds the called
// chaincode read set and write set to the calling transaction.
// If the called chaincode is on a different channel,
// only the Response is returned to the calling chaincode; any PutState calls
// from the called chaincode will not have any effect on the ledger; that is,
// the called chaincode on a different channel will not have its read set
// and write set applied to the transaction. Only the calling chaincode's
// read set and write set will be applied to the transaction. Effectively
// the called chaincode on a different channel is a `Query`, which does not
// participate in state validation checks in subsequent commit phase.
// If `channel` is empty, the caller's channel is assumed.
InvokeChaincode(chaincodeName string, args [][]byte, channel string) pb.Response
// GetState returns the value of the specified `key` from the
// ledger. Note that GetState doesn't read data from the writeset, which
// has not been committed to the ledger. In other words, GetState doesn't
// consider data modified by PutState that has not been committed.
// If the key does not exist in the state database, (nil, nil) is returned.
GetState(key string) ([]byte, error)
// PutState puts the specified `key` and `value` into the transaction's
// writeset as a data-write proposal. PutState doesn't effect the ledger
// until the transaction is validated and successfully committed.
// Simple keys must not be an empty string and must not start with null
// character (0x00), in order to avoid range query collisions with
// composite keys, which internally get prefixed with 0x00 as composite
// key namespace.
PutState(key string, value []byte) error
// DelState records the specified `key` to be deleted in the writeset of
// the transaction proposal. The `key` and its value will be deleted from
// the ledger when the transaction is validated and successfully committed.
DelState(key string) error
// GetStateByRange returns a range iterator over a set of keys in the
// ledger. The iterator can be used to iterate over all keys
// between the startKey (inclusive) and endKey (exclusive).
// The keys are returned by the iterator in lexical order. Note
// that startKey and endKey can be empty string, which implies unbounded range
// query on start or end.
// Call Close() on the returned StateQueryIteratorInterface object when done.
// The query is re-executed during validation phase to ensure result set
// has not changed since transaction endorsement (phantom reads detected).
GetStateByRange(startKey, endKey string) (StateQueryIteratorInterface, error)
// GetStateByPartialCompositeKey queries the state in the ledger based on
// a given partial composite key. This function returns an iterator
// which can be used to iterate over all composite keys whose prefix matches
// the given partial composite key. The `objectType` and attributes are
// expected to have only valid utf8 strings and should not contain
// U+0000 (nil byte) and U+10FFFF (biggest and unallocated code point).
// See related functions SplitCompositeKey and CreateCompositeKey.
// Call Close() on the returned StateQueryIteratorInterface object when done.
// The query is re-executed during validation phase to ensure result set
// has not changed since transaction endorsement (phantom reads detected).
GetStateByPartialCompositeKey(objectType string, keys []string) (StateQueryIteratorInterface, error)
// CreateCompositeKey combines the given `attributes` to form a composite
// key. The objectType and attributes are expected to have only valid utf8
// strings and should not contain U+0000 (nil byte) and U+10FFFF
// (biggest and unallocated code point).
// The resulting composite key can be used as the key in PutState().
CreateCompositeKey(objectType string, attributes []string) (string, error)
// SplitCompositeKey splits the specified key into attributes on which the
// composite key was formed. Composite keys found during range queries
// or partial composite key queries can therefore be split into their
// composite parts.
SplitCompositeKey(compositeKey string) (string, []string, error)
// GetQueryResult performs a "rich" query against a state database. It is
// only supported for state databases that support rich query,
// e.g.CouchDB. The query string is in the native syntax
// of the underlying state database. An iterator is returned
// which can be used to iterate (next) over the query result set.
// The query is NOT re-executed during validation phase, phantom reads are
// not detected. That is, other committed transactions may have added,
// updated, or removed keys that impact the result set, and this would not
// be detected at validation/commit time. Applications susceptible to this
// should therefore not use GetQueryResult as part of transactions that update
// ledger, and should limit use to read-only chaincode operations.
GetQueryResult(query string) (StateQueryIteratorInterface, error)
// GetHistoryForKey returns a history of key values across time.
// For each historic key update, the historic value and associated
// transaction id and timestamp are returned. The timestamp is the
// timestamp provided by the client in the proposal header.
// GetHistoryForKey requires peer configuration
// core.ledger.history.enableHistoryDatabase to be true.
// The query is NOT re-executed during validation phase, phantom reads are
// not detected. That is, other committed transactions may have updated
// the key concurrently, impacting the result set, and this would not be
// detected at validation/commit time. Applications susceptible to this
// should therefore not use GetHistoryForKey as part of transactions that
// update ledger, and should limit use to read-only chaincode operations.
GetHistoryForKey(key string) (HistoryQueryIteratorInterface, error)
// GetPrivateData returns the value of the specified `key` from the specified
// `collection`. Note that GetPrivateData doesn't read data from the
// private writeset, which has not been committed to the `collection`. In
// other words, GetPrivateData doesn't consider data modified by PutPrivateData
// that has not been committed.
GetPrivateData(collection, key string) ([]byte, error)
// PutPrivateData puts the specified `key` and `value` into the transaction's
// private writeset. Note that only hash of the private writeset goes into the
// transaction proposal response (which is sent to the client who issued the
// transaction) and the actual private writeset gets temporarily stored in a
// transient store. PutPrivateData doesn't effect the `collection` until the
// transaction is validated and successfully committed. Simple keys must not be
// an empty string and must not start with null character (0x00), in order to
// avoid range query collisions with composite keys, which internally get
// prefixed with 0x00 as composite key namespace.
PutPrivateData(collection string, key string, value []byte) error
// DelState records the specified `key` to be deleted in the private writeset of
// the transaction. Note that only hash of the private writeset goes into the
// transaction proposal response (which is sent to the client who issued the
// transaction) and the actual private writeset gets temporarily stored in a
// transient store. The `key` and its value will be deleted from the collection
// when the transaction is validated and successfully committed.
DelPrivateData(collection, key string) error
// GetPrivateDataByRange returns a range iterator over a set of keys in a
// given private collection. The iterator can be used to iterate over all keys
// between the startKey (inclusive) and endKey (exclusive).
// The keys are returned by the iterator in lexical order. Note
// that startKey and endKey can be empty string, which implies unbounded range
// query on start or end.
// Call Close() on the returned StateQueryIteratorInterface object when done.
// The query is re-executed during validation phase to ensure result set
// has not changed since transaction endorsement (phantom reads detected).
GetPrivateDataByRange(collection, startKey, endKey string) (StateQueryIteratorInterface, error)
// GetPrivateDataByPartialCompositeKey queries the state in a given private
// collection based on a given partial composite key. This function returns
// an iterator which can be used to iterate over all composite keys whose prefix
// matches the given partial composite key. The `objectType` and attributes are
// expected to have only valid utf8 strings and should not contain
// U+0000 (nil byte) and U+10FFFF (biggest and unallocated code point).
// See related functions SplitCompositeKey and CreateCompositeKey.
// Call Close() on the returned StateQueryIteratorInterface object when done.
// The query is re-executed during validation phase to ensure result set
// has not changed since transaction endorsement (phantom reads detected).
GetPrivateDataByPartialCompositeKey(collection, objectType string, keys []string) (StateQueryIteratorInterface, error)
// GetPrivateDataQueryResult performs a "rich" query against a given private
// collection. It is only supported for state databases that support rich query,
// e.g.CouchDB. The query string is in the native syntax
// of the underlying state database. An iterator is returned
// which can be used to iterate (next) over the query result set.
// The query is NOT re-executed during validation phase, phantom reads are
// not detected. That is, other committed transactions may have added,
// updated, or removed keys that impact the result set, and this would not
// be detected at validation/commit time. Applications susceptible to this
// should therefore not use GetQueryResult as part of transactions that update
// ledger, and should limit use to read-only chaincode operations.
GetPrivateDataQueryResult(collection, query string) (StateQueryIteratorInterface, error)
// GetCreator returns `SignatureHeader.Creator` (e.g. an identity)
// of the `SignedProposal`. This is the identity of the agent (or user)
// submitting the transaction.
GetCreator() ([]byte, error)
// GetTransient returns the `ChaincodeProposalPayload.Transient` field.
// It is a map that contains data (e.g. cryptographic material)
// that might be used to implement some form of application-level
// confidentiality. The contents of this field, as prescribed by
// `ChaincodeProposalPayload`, are supposed to always
// be omitted from the transaction and excluded from the ledger.
GetTransient() (map[string][]byte, error)
// GetBinding returns the transaction binding, which is used to enforce a
// link between application data (like those stored in the transient field
// above) to the proposal itself. This is useful to avoid possible replay
// attacks.
GetBinding() ([]byte, error)
// GetDecorations returns additional data (if applicable) about the proposal
// that originated from the peer. This data is set by the decorators of the
// peer, which append or mutate the chaincode input passed to the chaincode.
GetDecorations() map[string][]byte
// GetSignedProposal returns the SignedProposal object, which contains all
// data elements part of a transaction proposal.
GetSignedProposal() (*pb.SignedProposal, error)
// GetTxTimestamp returns the timestamp when the transaction was created. This
// is taken from the transaction ChannelHeader, therefore it will indicate the
// client's timestamp and will have the same value across all endorsers.
GetTxTimestamp() (*timestamp.Timestamp, error)
// SetEvent allows the chaincode to set an event on the response to the
// proposal to be included as part of a transaction. The event will be
// available within the transaction in the committed block regardless of the
// validity of the transaction.
SetEvent(name string, payload []byte) error
}