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 UUID
var AWS = require('aws-sdk');
var uuid = require('node-uuid');
// Create an S3 client
var s3 = new AWS.S3();
// Create a bucket and upload something into it
var 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~