Java calling Ethereum contract
The smart contract has been written for a long time
if they can add changes, the description is centralized
the contract is written into the Ethereum smart contract, which is a contradiction sentence
the financial customer service doesn't understand, which is very unreliable
community sites
what is Ethereum
Ethereum is often compared with bitcoin, but the situation is different. Bitcoin is a kind of cryptocurrency and distributed payment network, which allows bitcoin to be transferred between users
related: what is bitcoin? How does it work
Ethereum has a bigger goal. As Ethereum says, "Ethereum is a distributed platform running smart contracts.". These smart contracts run on "Ethereum virtual machine", a distributed computing network composed of all devices running Ethernet nodes
"distributed platform" means that anyone can set up and run an Ethereum node just as anyone can run a bitcoin node. Anyone who wants to run "smart contracts" on nodes must pay the operators of these nodes in ether, which is a cryptocurrency related to Ethereum. Therefore, the person running the Ethernet node provides computing power and gets paid in the Ethernet, which is similar to the way that the person running the bitcoin node provides hash power and pays in bitcoin
in other words, although bitcoin is only a blockchain and payment network, Ethereum is a distributed computing network, and its blockchain can be used for many other things. Details are provided in the Ethereum white paper
what is ether
Ethernet is a digital token (or cryptocurrency) related to Ethereum blockchain. In other words, Ethereum is the token and Ethereum is the platform. But now people often use these terms alternately. For example, coinbase allows you to buy Ethereum, which stands for Ethereum
this is technically "altcoin", which actually means a non bitcoin cryptocurrency. Like bitcoin, ether is supported by distributed blockchain - in this case, Ethereum blockchain
developers who want to create applications or Ethereum smart contracts on Ethereum blockchain need Ethernet token to pay for nodes to host it, while users of Ethereum based applications may need Ethernet to pay for services in these applications. People can also sell services outside the Ethereum network and accept Ethernet payments, or they can sell Ethernet tokens in cash - just like bitcoin
Yes, refer to the interaction between contracts. Digital currency exchange platform for example, I am trying to sign a smart contract from another factory contract and then redeploy the address of the new smart contract. However, the address it returns is the transaction hash, not the contract address. I believe this is because when the address is returned, the contract has not been exploited. When I deploy the smart contract with Web3, it seems that it will not output the contract address until the smart contract is deployed
Ruitai coin has not been launched on the third-party platform, but it is rumored that it will also be launched on the third-party platform.
Generally speaking, the steps of deploying smart contract are as follows:
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start an Ethereum node (such as geth or testrpc)
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use Solc to compile smart contracts=& gt; Get the binary code
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deploy the compiled contract to the network This step will consume Ethernet currency, and you need to use the default address or specified address of your node to sign the contract.)=& gt; Get the blockchain address and ABI of the contract (JSON representation of the contract interface, including variables, events and callable methods) The author confused ABI with contract interface here. ABI is the binary representation of the contract interface.)
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use the JavaScript API provided by web3.js to call the contract Depending on the type of call, it may consume Ethernet currency.)
like many other languages, when accessing state variables, it is not necessary to add a prefix such as this
this contract can't do a lot (limited by Ethereum's infrastructure), it just allows anyone to store a number. And anyone in the world can access this number. There is no reliable way to protect the number you publish. Anyone can call the set method to set a different number to cover your published number. But your numbers will remain in the history of blockchain. Later we'll learn how to add an access limit so that only you can change the number
token example
the next contract will implement a cryptocurrency in the simplest form. Taking money in the air is no longer a magic trick. Of course, only the person who creates the contract can do it (it's also very easy to use other currency issuance modes, just to realize the differences in details). And anyone can send money to others, without registering a user name and password, as long as there is a pair of Ethereum public and private keys
note
this is not a good example for online solidness environments. If you use the online solidity environment to try this example. The address of from cannot be changed when the function is called. So you can only play the role of a coiner, you can cast money and send it to others, but you can't play the role of others. This online solidity environment will be improved in the future.
Solidness language is a special language for writing and executing smart contracts. It is a contract oriented high-level language running on the basis of Ethereum virtual machine. It was first proposed by the former CTO and co-founder Gavin wood of Ethereum in August 2014. Later, Ethereum developers set up a special team to continuously improve solidness language, At present, it is still under development and optimization. The development storage area on GitHub is HTPs / github.com/thereum/solidness. Here we can learn the most comprehensive details and related documents about the development and iteration process of solidness language. In terms of language style, solid language is deeply influenced by C + +, Python and JavaScript. It is a static programming language, compiled in bytecode mode, so it can run on Ethereum virtual machine. Gavin wood uses the syntax rules of ECMAScript scripting language of JavaScript for reference when developing solid language, which makes it somewhat similar to the existing web development language, but it is quite different. For example, solid language has static type, variable return function and so on. The most important point is that solid language can write contracts with self executing business logic and embedded in smart contracts. Therefore, it is not only one of the basic programming languages of Ethereum, but also the basic programming languages of most other Ethereum based blockchain procts (blockchain 2.0) with smart contracts, It is widely used in the vast majority of blockchain procts, such as hyperledger project, which is developed with soliditv language
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