Nodejs课堂笔记-第五课 在nodejs中使用DynamoDB Local

从博客园搬到了CSDN，具体原因就不明说了，简单一句话就是原创被当抄袭，这种感觉很不爽。

好了，我们继续开始学习历程吧。在第四课中，我们介绍了DynamoDB Local版本的使用方式。这节课中，我们开始在nodejs中使用DynamoDB。

在Amazon的网站中，提供了一个DynamoDB的sample，请看下面：

// Load the SDK and UUIDvar AWS = require('aws-sdk');var uuid = require('node-uuid');// Create an S3 clientvar s3 = new AWS.S3();// Create a bucket and upload something into itvar bucketName = 'node-sdk-sample-' + uuid.v4();var keyName = 'hello_world.txt';s3.createBucket({Bucket: bucketName}, function() {  var params = {Bucket: bucketName, Key: keyName, Body: 'Hello World!'};  s3.putObject(params, function(err, data) {    if (err)      console.log(err)    else      console.log("Successfully uploaded data to " + bucketName + "/" + keyName);  });});

这段示例代码直接使用的DynamoDB Web Service，而不是DynamoDB Local服务。和我们的需求不太一样，所以再次研究Amazon的API文档。

看到dynamodb在使用之前需要配置amazon账户，点击这里查看配置说明。 按照文档中的说明，我们补充下面的配置代码：

/* Auth Config */AWS.config.update({    aws_access_key_id : "andy-aws-account",    aws_secret_access_key : "andy-aws-account",    region : "eu-west-1"})

在第四课中提到过，当使用local模式时，账户信息都会被忽略。因此输入任意账户信息都可以。

下一步就是创建一个指向local的endpoint，我们使用下面代码进行创建：

dyn= new AWS.DynamoDB({ endpoint: new AWS.Endpoint('http://localhost:8000') });

当endpoint创建成功后，就相当于获取了一个dynamodb的实例，下面就可以执行SQL操作了。我们首先做一个简单的操作：创建一张表，再查询所有表。

在dynamodb的api中，创建表的API是(点击这里，查看API文档)：

createTable(params = {}, callback) ⇒ AWS.Request

需要给createTable传递一个参数对象，这个参数对象有些复杂：

var params = {  AttributeDefinitions: [ /* required */    {      AttributeName: 'STRING_VALUE', /* required */      AttributeType: 'S | N | B' /* required */    },    /* more items */  ],  KeySchema: [ /* required */    {      AttributeName: 'STRING_VALUE', /* required */      KeyType: 'HASH | RANGE' /* required */    },    /* more items */  ],  ProvisionedThroughput: { /* required */    ReadCapacityUnits: 0, /* required */    WriteCapacityUnits: 0 /* required */  },  TableName: 'STRING_VALUE', /* required */  GlobalSecondaryIndexes: [    {      IndexName: 'STRING_VALUE', /* required */      KeySchema: [ /* required */        {          AttributeName: 'STRING_VALUE', /* required */          KeyType: 'HASH | RANGE' /* required */        },        /* more items */      ],      Projection: { /* required */        NonKeyAttributes: [          'STRING_VALUE',          /* more items */        ],        ProjectionType: 'ALL | KEYS_ONLY | INCLUDE'      },      ProvisionedThroughput: { /* required */        ReadCapacityUnits: 0, /* required */        WriteCapacityUnits: 0 /* required */      }    },    /* more items */  ],  LocalSecondaryIndexes: [    {      IndexName: 'STRING_VALUE', /* required */      KeySchema: [ /* required */        {          AttributeName: 'STRING_VALUE', /* required */          KeyType: 'HASH | RANGE' /* required */        },        /* more items */      ],      Projection: { /* required */        NonKeyAttributes: [          'STRING_VALUE',          /* more items */        ],        ProjectionType: 'ALL | KEYS_ONLY | INCLUDE'      }    },    /* more items */  ],  StreamSpecification: {    StreamEnabled: true || false,    StreamViewType: 'NEW_IMAGE | OLD_IMAGE | NEW_AND_OLD_IMAGES | KEYS_ONLY'  }};

嗯。 这里感觉需要对amazon的文档做些吐槽。为啥这个文档里面的参数，比如S|B|N是什么意思，NEW_IMAGE,OLD_IMAGE 是什么意思也没有说明。只看上面的说明，感觉跟没说是一样的。

再经历了多次失败之后，终于写出了下面验证通过的param：

/* Create A Table*/var params = {    AttributeDefinitions: [ /* required */        {            AttributeName: 'ID', /* required */            AttributeType: 'S' /* required */        },        {            AttributeName: 'NAME', /* required */            AttributeType: 'S' /* required */        }        /* more items */    ],    TableName: 'DNMDB', /* required */    KeySchema: [ /* required */        {            AttributeName: 'ID', /* required */            KeyType: 'HASH' /* required */        },        {            AttributeName: "NAME",            KeyType: "RANGE"        }        /* more items */    ],    LocalSecondaryIndexes: [        {            IndexName: 'Index1', /* required */            KeySchema: [ /* required */                {                    AttributeName: 'ID', /* required */                    KeyType: 'HASH' /* required */                },                {                    AttributeName: 'NAME', /* required */                    KeyType: 'RANGE' /* required */                }                /* more items */            ],            Projection: { /* required */                NonKeyAttributes: [                    'ID'                    /* more items */                ],                ProjectionType: 'INCLUDE'            }        }        /* more items */    ],    StreamSpecification: {        StreamEnabled: true,        StreamViewType: 'NEW_IMAGE'    },    ProvisionedThroughput: { /* required */        ReadCapacityUnits: 1, /* required */        WriteCapacityUnits: 1 /* required */    },    GlobalSecondaryIndexes: [        {            IndexName: 'GIND1', /* required */            KeySchema: [ /* required */                {                    AttributeName: 'ID', /* required */                    KeyType: 'HASH' /* required */                },                /* more items */            ],            Projection: { /* required */                NonKeyAttributes: [                    'NAME'                    /* more items */                ],                ProjectionType: 'INCLUDE'            },            ProvisionedThroughput: { /* required */                ReadCapacityUnits: 1, /* required */                WriteCapacityUnits: 1 /* required */            }        }        /* more items */    ]};

然后我们将params传递给createTable函数，因为创建表是异步操作，当开始创建表时，table的状态会是CREATEING，只有创建完毕之后，才会变成ACTIVE。
代码如下：

dyn.createTable(params, function(err, data) {    if (err) console.log(err, err.stack); // an error occurred    else     console.log(data);           // successful response})

而查询表的API就显得简单了

listTables(params = {}, callback) ⇒ AWS.Request

代码原样拷贝过来：

dyn.listTables(function (err, data){    console.log('listTables',err,data);});

OK,一个非常简单使用DynamoDB Local的demo就完成了，完整代码如下:

/** * Created by andy on 2015/9/11. */var AWS = require('aws-sdk');var uuid = require('node-uuid');/* Auth Config */AWS.config.update({    aws_access_key_id : "andy-aws-account",    aws_secret_access_key : "andy-aws-account",    region : "eu-west-1"})dyn= new AWS.DynamoDB({ endpoint: new AWS.Endpoint('http://localhost:8000') });/* Create A Table*/var params = {    AttributeDefinitions: [ /* required */        {            AttributeName: 'ID', /* required */            AttributeType: 'S' /* required */        },        {            AttributeName: 'NAME', /* required */            AttributeType: 'S' /* required */        }        /* more items */    ],    TableName: 'DNMDB', /* required */    KeySchema: [ /* required */        {            AttributeName: 'ID', /* required */            KeyType: 'HASH' /* required */        },        {            AttributeName: "NAME",            KeyType: "RANGE"        }        /* more items */    ],    LocalSecondaryIndexes: [        {            IndexName: 'Index1', /* required */            KeySchema: [ /* required */                {                    AttributeName: 'ID', /* required */                    KeyType: 'HASH' /* required */                },                {                    AttributeName: 'NAME', /* required */                    KeyType: 'RANGE' /* required */                }                /* more items */            ],            Projection: { /* required */                NonKeyAttributes: [                    'ID'                    /* more items */                ],                ProjectionType: 'INCLUDE'            }        }        /* more items */    ],    StreamSpecification: {        StreamEnabled: true,        StreamViewType: 'NEW_IMAGE'    },    ProvisionedThroughput: { /* required */        ReadCapacityUnits: 1, /* required */        WriteCapacityUnits: 1 /* required */    },    GlobalSecondaryIndexes: [        {            IndexName: 'GIND1', /* required */            KeySchema: [ /* required */                {                    AttributeName: 'ID', /* required */                    KeyType: 'HASH' /* required */                },                /* more items */            ],            Projection: { /* required */                NonKeyAttributes: [                    'NAME'                    /* more items */                ],                ProjectionType: 'INCLUDE'            },            ProvisionedThroughput: { /* required */                ReadCapacityUnits: 1, /* required */                WriteCapacityUnits: 1 /* required */            }        }        /* more items */    ]};dyn.createTable(params, function(err, data) {    if (err) console.log(err, err.stack); // an error occurred    else     console.log(data);           // successful response})dyn.listTables(function (err, data){    console.log('listTables',err,data);});

第一次执行时，因为createtable是异步操作，所以查询表会报空. 而createTable会返回所创建表的信息：

listTables null { TableNames: [] }{ TableDescription:    { AttributeDefinitions: [ [Object], [Object] ],     TableName: 'DNMDB',     KeySchema: [ [Object], [Object] ],     TableStatus: 'ACTIVE',     CreationDateTime: Fri Sep 11 2015 19:49:41 GMT+0800 (China Standard Time),     ProvisionedThroughput:       { LastIncreaseDateTime: Thu Jan 01 1970 08:00:00 GMT+0800 (China Standard Time),        LastDecreaseDateTime: Thu Jan 01 1970 08:00:00 GMT+0800 (China Standard Time),        NumberOfDecreasesToday: 0,        ReadCapacityUnits: 1,        WriteCapacityUnits: 1 },     TableSizeBytes: 0,     ItemCount: 0,     TableArn: 'arn:aws:dynamodb:ddblocal:000000000000:table/DNMDB',     LocalSecondaryIndexes: [ [Object] ],     GlobalSecondaryIndexes: [ [Object] ],     StreamSpecification: { StreamEnabled: true, StreamViewType: 'NEW_IMAGE' },     LatestStreamLabel: '2015-09-11T11:49:41.684',     LatestStreamArn: 'arn:aws:dynamodb:ddblocal:000000000000:table/DNMDB/stream/2015-09-11T11:49:41.684' } }

第二次执行，就可以查询表名了。如下：

listTables null { TableNames: [ 'DNMDB' ] }

虽然表创建成功了，但创建表的各项参数还是没搞明白。功夫不负有心人，终于找到了相关参数说明。
可今天是周五了，还是早点下课过周末吧。 各项参数说明，留待下节课再讲。OK，下课，起立~