Add initial template and demo code for project

Author: Anna Spysz

samconfig.toml

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+version = 0.1
+[default.global.parameters]
+stack_name = "aws-app-composer-basic-api"
+[default.deploy.parameters]
+capabilities = "CAPABILITY_IAM"

src/CreateUser/index.js

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+const { randomUUID } = require("crypto");
+const { DynamoDBClient } = require("@aws-sdk/client-dynamodb");
+const { DynamoDBDocumentClient, PutCommand } = require("@aws-sdk/lib-dynamodb");
+
+const client = new DynamoDBClient({});
+const ddbDocClient = DynamoDBDocumentClient.from(client);
+
+
+exports.handler = async event => {
+  try {
+    // Log the event argument for debugging and for use in local development.
+    console.log(JSON.stringify(event, undefined, 2));
+
+    const item = JSON.parse(event.body);
+
+    // We generate a random ID to prevent collisions and distribute records in the
+    // DynamoDB Table keyspace.
+    if ("id" in item) {
+      return {
+        statusCode: 400,
+        body: "'id' may not be provided in item attributes"
+      };
+    }
+
+    // Generate a random UUID as the hash key ID for the item
+    item.id = randomUUID();
+
+    console.log(`Adding item with ID '${item.id}' to table '${({}).ITEMS_TABLE_NAME}' with attributes: ${JSON.stringify(item, null, 2)}`);
+
+    // We use a ConditionExpression to ensure we don't overwrite a record that
+    // already exists for the same id. An error will be thrown if this happens
+    // and we'll return a 500 error.
+    const command = new PutCommand({
+      TableName: ({}).ITEMS_TABLE_NAME,
+      Item: item,
+      ConditionExpression: "#idKey <> :idValue",
+      ExpressionAttributeNames: {
+        "#idKey": "id"
+      },
+      ExpressionAttributeValues: {
+        ":idValue": item.id
+      }
+    });
+
+    await ddbDocClient.send(command);
+
+    console.log(`Successfully saved item '${item.id}'`);
+
+    return {
+      statusCode: 200
+    };
+  } catch (e) {
+    console.error(`Failed to save item: ${e.message} (${e.constructor.name})`);
+
+    return {
+      statusCode: 500,
+      body: "Internal Service Error"
+    };
+  }
+};

src/CreateUser/package.json

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+{
+  "name": "function",
+  "version": "1.0.0"
+}

src/DeleteUser/index.js

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+const { DynamoDBClient } = require("@aws-sdk/client-dynamodb");
+const { DynamoDBDocumentClient, DeleteCommand } = require("@aws-sdk/lib-dynamodb");
+
+const client = new DynamoDBClient({});
+const ddbDocClient = DynamoDBDocumentClient.from(client);
+
+exports.handler = async event => {
+  try {
+    // Log the event argument for debugging and for use in local development.
+    console.log(JSON.stringify(event, undefined, 2));
+
+    const id = event.pathParameters.id;
+
+    console.log(`Deleting item with ID '${id}' from table '${({}).ITEMS_TABLE_NAME}'`);
+
+    // When deleting the record, return its values to us so we can see if the
+    // record actually existed
+    const command = new DeleteCommand({
+      TableName: ({}).ITEMS_TABLE_NAME,
+      Key: { id },
+      ReturnValues: "ALL_OLD"
+    });
+
+    const response = await ddbDocClient.send(command);
+
+    // If we deleted an item, Attributes will have its old attributes.
+    // Otherwise, Attributes will be null.
+    if (response.Attributes) {
+      console.log(`Item '${id}' deleted`);
+
+      return {
+        statusCode: 200
+      };
+    } else {
+      console.log(`Item '${id}' not found`);
+
+      return {
+        statusCode: 404,
+        body: "Item not found"
+      };
+    }
+  } catch (e) {
+    console.error(`Failed to delete item: ${e.message} (${e.constructor.name})`);
+
+    return {
+      statusCode: 500,
+      body: `Internal Service Error`
+    };
+  }
+};

src/DeleteUser/package.json

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+{
+  "name": "function",
+  "version": "1.0.0"
+}

src/GetUser/index.js

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+const { DynamoDBClient } = require("@aws-sdk/client-dynamodb");
+const { DynamoDBDocumentClient, GetCommand } = require("@aws-sdk/lib-dynamodb");
+
+const client = new DynamoDBClient({});
+const ddbDocClient = DynamoDBDocumentClient.from(client);
+
+exports.handler = async event => {
+  try {
+    // Log the event argument for debugging and for use in local development.
+    console.log(JSON.stringify(event, undefined, 2));
+
+    const id = event.pathParameters.id;
+
+    console.log(`Getting item with ID '${id}' from table '${({}).ITEMS_TABLE_NAME}'`);
+
+    const command = new GetCommand({
+      TableName: ({}).ITEMS_TABLE_NAME,
+      Key: { id }
+    });
+
+    const response = await ddbDocClient.send(command);
+
+    if (response.Item) {
+      console.log(`Retrieved item '${id}' with attributes ${JSON.stringify(response.Item)}`);
+
+      return {
+        statusCode: 200,
+        body: JSON.stringify({
+          item: response.Item
+        })
+      };
+    } else {
+      console.log(`No item found with id '${id}'`);
+
+      return {
+        statusCode: 404,
+        body: "Item not found"
+      };
+    }
+  } catch (e) {
+    console.error(`Failed to get item: ${e.message} (${e.constructor.name})`);
+
+    return {
+      statusCode: 500,
+      body: "Internal Service Error"
+    };
+  }
+};

src/GetUser/package.json

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+{
+  "name": "function",
+  "version": "1.0.0"
+}

src/ListUsers/index.js

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+const { DynamoDBClient, ScanCommand } = require("@aws-sdk/client-dynamodb");
+
+const client = new DynamoDBClient({});
+
+exports.handler = async event => {
+  try {
+    // Log the event argument for debugging and for use in local development.
+    console.log(JSON.stringify(event, undefined, 2));
+
+    console.log(`Listing items from table '${({}).ITEMS_TABLE_NAME}'`);
+
+    let ids = [];
+
+    // Loop over all items. If there are more items after a request, the
+    // response LastEvaluatedKey will have a non-null value that we can
+    // pass in the next request to continue fetching more items.
+    let lastEvaluatedKey;
+    do {
+      const command = new ScanCommand({
+        TableName: ({}).ITEMS_TABLE_NAME,
+        ProjectionExpression: "id",
+        ExclusiveStartKey: lastEvaluatedKey
+      });
+
+      const response = await client.send(command);
+
+      const additionalIds = response.Items.map(item => item.id);
+
+      ids = [...ids, ...additionalIds];
+
+      lastEvaluatedKey = response.LastEvaluatedKey;
+    } while (lastEvaluatedKey);
+
+    console.log(`Successfully scanned for list of IDs: ${JSON.stringify(ids, null, 2)}`);
+
+    return {
+      statusCode: 200,
+      body: JSON.stringify({
+        ids
+      })
+    };
+  } catch (e) {
+    console.error(`Failed to list items: ${e.message} (${e.constructor.name})`);
+
+    return {
+      statusCode: 500,
+      body: "Internal Service Error"
+    };
+  }
+};

src/ListUsers/package.json

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+{
+  "name": "function",
+  "version": "1.0.0"
+}

src/UpdateUser/index.js

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+const { DynamoDBClient, ConditionalCheckFailedException } = require("@aws-sdk/client-dynamodb");
+const { DynamoDBDocumentClient, PutCommand } = require("@aws-sdk/lib-dynamodb");
+
+const client = new DynamoDBClient({});
+const ddbDocClient = DynamoDBDocumentClient.from(client);
+
+exports.handler = async event => {
+  try {
+    // Log the event argument for debugging and for use in local development.
+    console.log(JSON.stringify(event, undefined, 2));
+
+    const item = JSON.parse(event.body);
+
+    if ("id" in item) {
+      return {
+        statusCode: 400,
+        body: "'id' may not be provided in item attributes"
+      };
+    }
+
+    item.id = event.pathParameters.id;
+
+    console.log(`Updating item with ID '${item.id}' in table '${({}).ITEMS_TABLE_NAME}'`);
+
+    // Use a ConditionExpression to overwrite a record only if there is
+    // already a record (i.e. there already is a record with an id attribute,
+    // because all records must have a hash key attribute)
+    const command = new PutCommand({
+      TableName: ({}).ITEMS_TABLE_NAME,
+      Item: item,
+      ConditionExpression: "attribute_exists(#idKey)",
+      ExpressionAttributeNames: {
+        "#idKey": "id"
+      }
+    });
+
+    await ddbDocClient.send(command);
+
+    console.log(`Successfully updated item '${item.id}'`);
+
+    return {
+      statusCode: 200
+    };
+  } catch (e) {
+    if (e instanceof ConditionalCheckFailedException) {
+      console.log("Item not found");
+
+      return {
+        statusCode: 404,
+        body: "Item not found"
+      };
+    }
+
+    console.error(`Failed to update item: ${e.message} (${e.constructor.name})`);
+
+    return {
+      statusCode: 500,
+      body: "Internal Service Error"
+    };
+  }
+};

src/UpdateUser/package.json

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+{
+  "name": "function",
+  "version": "1.0.0"
+}