JAVA-AWS Cognito-检查Cognito用户池中是否存在用户

Question

我想允许用户在字段中输入他们的用户名/密码。继续后，我想运行一个检查，看看该用户是否已经存在于用户池中。如果他们这样做了，请登录并继续使用应用程序，如果他们不这样做，则转到帐户创建流程，在那里他们将被指示添加姓名、电话号码、电子邮件等。

我找不到关于如何使用AWS Cognito让用户登录的文档。我应该能够在呼叫中传递用户名/密码，并得到一个回复，说用户存在/用户不存在或其他什么！我是不是遗漏了什么？

如有任何帮助，我们将不胜感激。我查过文件了。。。

Answer 1

要检查用户是否存在，只需要用户名。

因此，对于您的场景，在用户输入用户名和密码后触发下面的myMethod()。这将

1. 检查用户名是否已在用户中
2. 如果用户名存在，请执行登录
3. 如果用户名不存在，请创建帐户

---

/**
* let's say you call this method when user enters username and password
* @param context context
* @param identityProvider cognito client
* @param username user entered username
* @param password user entered password
* @return
*/
private void myMethod(Context context, AWSCognitoIdentityProvider identityProvider, String username, String password) {

boolean userExists = userExists(context, identityProvider, username);

if(userExists) {
// perform sign in with provided password
} else {
// create account
}
}

/**
* @param context context
* @param identityProvider cognito client
* @param username user entered username
* @return true if username is already in use, false otherwise
*/
private boolean userExists(Context context, AWSCognitoIdentityProvider identityProvider, String username) {
LambdaLogger logger = context.getLogger();
try {
AdminGetUserRequest getUserRequest = new AdminGetUserRequest();
getUserRequest.setUserPoolId("cognitoPoolId");
getUserRequest.setUsername(username);
AdminGetUserResult getUserResult = identityProvider.adminGetUser(getUserRequest);
return true;
} catch (UserNotFoundException userNotFoundException) {
logger.log("UserNotFoundException! " + userNotFoundException.toString());
return false;
} catch (Exception e) {
return false;
}
}

Answer 2

我不必每次都对Cognito用户池进行全面扫描，而是使用Cognito的功能来触发事件。对于您的用例，Cognito可以运行Lambda。您对"迁移用户"触发器感兴趣。基本上，当用户试图通过Cognito登录到您的系统，并且池中不存在该用户时，会触发一个触发器，让您登录该用户并将其迁移到Cognito。

收到的数据看起来像：

{
"version": "1",
"triggerSource": "UserMigration_Authentication",
"region": "us-west-2",
"userPoolId": "us-west-2_abcdef",
"userName": "[e-mail]",
"callerContext": {
"awsSdkVersion": "aws-sdk-unknown-unknown",
"clientId": "yourclientid"
},
"request": {
"password": "theuserpassword",
"validationData": null,
"userAttributes": null
},
"response": {
"userAttributes": null,
"forceAliasCreation": null,
"finalUserStatus": null,
"messageAction": null,
"desiredDeliveryMediums": null
}
}

您的Lambda将使用此信息，并最终获取用户名和密码并确定其是否有效。如果是，您将在response.userAttributes字段中返回信息，以及是否要发送Cognito欢迎电子邮件(messageAction(和其他一些值。例如，您可以发回：

{
"version": "1",
"triggerSource": "UserMigration_Authentication",
"region": "us-west-2",
"userPoolId": "us-west-2_abcdef",
"userName": "[e-mail]",
"callerContext": {
"awsSdkVersion": "aws-sdk-unknown-unknown",
"clientId": "yourclientid"
},
"request": {
"password": "theuserpassword",
"validationData": null,
"userAttributes": null
},
"response": {
"userAttributes": { "email":"[e-mail]",
"email_verified": "true" }
"forceAliasCreation": null,
"finalUserStatus": "CONFIRMED",
"messageAction": "SUPPRESS",
"desiredDeliveryMediums": null
}
}

你的Lambda在Java:中会是这样的

public class MigrateUserLambda implements RequestStreamHandler {
public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context) throws IOException {
LambdaLogger logger = context.getLogger();
ObjectMapper objectMapper = new ObjectMapper();
JsonNode rootNode = objectMapper.readTree(inputStream);
logger.log("input is " + objectMapper.writeValueAsString(rootNode));
String email = rootNode.path("email").asText();
String password = rootNode.path("request").path("password").asText();
// verify user name and password in MySQL.  If ok...
String triggerSource = rootNode.path("triggerSource").asText();
if( triggerSource.equals("UserMigration_Authentication")) {
JsonNode responseNode = rootNode.path("response");
if (responseNode != null) {
((ObjectNode) responseNode).with("userAttributes").put("username", "[e-mail]" );
((ObjectNode) responseNode).with("userAttributes").put("email_verified", "true" );
((ObjectNode) responseNode).put("messageAction", "SUPPRESS");
((ObjectNode) responseNode).put("finalUserStatus", "CONFIRMED");
}
}
String output = objectMapper.writeValueAsString(rootNode);
OutputStreamWriter writer = new OutputStreamWriter(outputStream, StandardCharsets.UTF_8);
writer.write(output);
logger.log("sending back " + output);
writer.close();
}
}

Answer 3

要列出用户，可以使用AWS Java SDK:

public static void list() {
AwsBasicCredentials awsCreds = AwsBasicCredentials.create(AWS_KEY,
AWS_SECRET);
CognitoIdentityProviderClient identityProviderClient =
CognitoIdentityProviderClient.builder()
.credentialsProvider(StaticCredentialsProvider.create(awsCreds))
.region(Region.of(REGION))
.build();
final ListUsersRequest listUsersRequest = ListUsersRequest.builder()
.userPoolId(POOL_ID)
.build();
ListUsersResponse result = identityProviderClient.listUsers(listUsersRequest);
System.out.println("Has users:"+result.hasUsers());
result.users().stream().map(u->u.username()).forEach(System.out::println);
}

它需要下一个依赖项(请使用最新版本(：

<dependency>
<groupId>software.amazon.awssdk</groupId>
<artifactId>aws-core</artifactId>
<version>2.13.57</version>
</dependency>
<dependency>
<groupId>software.amazon.awssdk</groupId>
<artifactId>cognitoidentityprovider</artifactId>
<version>2.13.57</version>
</dependency>

下面是一个关于如何从Java登录用户的代码示例。