要登录AWS Web应用，可以使用AWS SDK来实现。以下是使用Java的AWS SDK示例代码：

import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.services.securitytoken.AWSSecurityTokenServiceClient;
import com.amazonaws.services.securitytoken.model.AssumeRoleRequest;
import com.amazonaws.services.securitytoken.model.AssumeRoleResult;
import com.amazonaws.services.securitytoken.model.Credentials;
import com.amazonaws.services.securitytoken.model.GetFederationTokenRequest;
import com.amazonaws.services.securitytoken.model.GetFederationTokenResult;
import com.amazonaws.services.securitytoken.model.GetSessionTokenRequest;
import com.amazonaws.services.securitytoken.model.GetSessionTokenResult;

public class AwsLoginExample {
    public static void main(String[] args) {
        // 使用基本的AWS凭证进行登录
        BasicAWSCredentials credentials = new BasicAWSCredentials("ACCESS_KEY", "SECRET_KEY");
        
        // 使用AssumeRole进行登录
        AWSSecurityTokenServiceClient stsClient = new AWSSecurityTokenServiceClient(credentials);
        AssumeRoleRequest assumeRequest = new AssumeRoleRequest()
                .withRoleArn("ROLE_ARN")
                .withRoleSessionName("SESSION_NAME");
        AssumeRoleResult assumeResult = stsClient.assumeRole(assumeRequest);
        Credentials stsCredentials = assumeResult.getCredentials();
        
        // 使用GetFederationToken进行登录
        GetFederationTokenRequest federationTokenRequest = new GetFederationTokenRequest()
                .withName("USER_NAME")
                .withPolicy("POLICY");
        GetFederationTokenResult federationTokenResult = stsClient.getFederationToken(federationTokenRequest);
        Credentials federationTokenCredentials = federationTokenResult.getCredentials();
        
        // 使用GetSessionToken进行登录
        GetSessionTokenRequest sessionTokenRequest = new GetSessionTokenRequest()
                .withDurationSeconds(SESSION_DURATION);
        GetSessionTokenResult sessionTokenResult = stsClient.getSessionToken(sessionTokenRequest);
        Credentials sessionTokenCredentials = sessionTokenResult.getCredentials();
        
        // 使用获取到的凭证进行登录到AWS Web应用
        // ...
    }
}

以上代码示例提供了使用基本的AWS凭证、AssumeRole、GetFederationToken和GetSessionToken这四种方式进行AWS登录的示例。具体使用哪种方式取决于你的需求和权限。根据你的需要选择合适的方式，并替换示例代码中的参数和凭证信息。