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I have NOT worked on Java, SpringBoot and Maven a lot. I had gone through several posts for the issue mentioned above, but nothing was close to my scenario

I compile and package SpringBoot project using Maven with JDK1.8.0_172 on Windows 10

I then deploy this packaged war to Linux server (RHEL with JDK1.8.0_201 and Tomcat 8)

When I hit the URL http://localhost:8080/MyApp, tomcat errors and I don’t see anything wrong in Tomcat logs

I am not sure what I am doing wrong. Any help is highly appreciated

Error from Tomcat Server

The origin server did not find a current representation for the target resource or is not willing to disclose that one exists.

POM.xml file

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.htc.myapp.main</groupId>
  <artifactId>SpringProject</artifactId>
  <version>0.0.1-SNAPSHOT</version> 
  <properties>
    <java.version>1.8</java.version>
  </properties>
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.4.RELEASE</version>
  </parent>
  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>


<dependency>
<groupId>com.bmc.remedy</groupId>
<artifactId>remedyapi</artifactId>
<version>8.1</version>
<scope>system</scope>
<systemPath>${basedir}/lib/remedyapi-8.1.jar</systemPath>
</dependency>

    <!-- JSTL tag lib -->
    <dependency>
      <groupId>javax.servlet.jsp.jstl</groupId>
      <artifactId>javax.servlet.jsp.jstl-api</artifactId>
      <version>1.2.1</version>
    </dependency>

    <dependency>
      <groupId>taglibs</groupId>
      <artifactId>standard</artifactId>
      <version>1.1.2</version>
    </dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.data/spring-data-jpa -->
<!-- <dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-jpa</artifactId>
</dependency> -->   

    <!-- Tomcat for JSP rendering -->
    <dependency>
      <groupId>org.apache.tomcat.embed</groupId>
      <artifactId>tomcat-embed-jasper</artifactId>
      <scope>provided</scope>
    </dependency>

   <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>


             <dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-jdbc</artifactId>
    <version>4.3.8.RELEASE</version>
</dependency>

 <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.9</version>
        </dependency>


    <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.8.5</version>
        </dependency>



            <dependency>
            <groupId>net.sourceforge.jtds</groupId>
            <artifactId>jtds</artifactId>
            <version>1.3.1</version>
        </dependency>

    <dependency> 
        <groupId>javax.xml.bind</groupId>
        <artifactId>jaxb-api</artifactId>
        <version>2.3.0</version>
    </dependency>

    <!-- <dependency>
            <groupId>net.sourceforge.jtds</groupId>
            <artifactId>jtds</artifactId>
            <version>1.3.1</version>
        </dependency> -->
    <!--    
    <dependency> 
        <groupId>javax.xml.bind</groupId>
        <artifactId>jaxb-api</artifactId>
        <version>2.3.0</version>
    </dependency> -->



    <dependency>
        <groupId>javax.servlet.jsp</groupId>
        <artifactId>jsp-api</artifactId>
        <version>2.1</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>

    <dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.3</version>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency> 


<!-- <dependency> 
        <groupId>com.fasterxml.jackson.core</groupId> 
        <artifactId>jackson-databind</artifactId> 
        <version>2.5.3</version>  
</dependency>  -->



<!-- https://mvnrepository.com/artifact/com.sun.jersey/jersey-client -->
<dependency>
    <groupId>com.sun.jersey</groupId>
    <artifactId>jersey-client</artifactId>
    <version>1.19</version>
</dependency>

  <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-cache</artifactId>
        </dependency>



  </dependencies>

  <build>
  <finalName>MyApp</finalName>
    <plugins> 
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>


    <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>

            </plugin>

     </plugins>

  </build>
  <procedure><packaging>war</packaging></properties>
</project>

EDIT

I installed Tomcat 7 and was able to open the application. However, invoking some action on application throws ‘Something went wrong’

Looking into Tomcat logs it appears there’s some issue with DB connectivity

Error on Logs

2019-06-19 12:42:55.943 ERROR 20177 --- [bio-8080-exec-3] o.a.tomcat.jdbc.pool.ConnectionPool      : Unable to create initial connections of pool.
java.sql.SQLException: No suitable driver found for jdbc:jtds:sqlserver://10.xxx.xxx.xxx:1433/MyDatabase;user=username;password=pwd

I copied jtds-1.3.1.jar to $TOMCAT_instance/lib directory and also tried used the following DB settings but NOTHING worked

db_LMS.url=jdbc:jtds:sqlserver://10.xxx.xxx.xxx:1433;databaseName=MyDatabase;integratedSecurity=true;user=username;password=pwd
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

        db_LMS.url=jdbc:jtds:sqlserver://10.xxx.xxx.xxx:1433/MyDatabase;user=username;password=pwd
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

Any help on this issue is highly appreciated

Same-Origin Policy (SOP)

With SOP in place, access to cross-origin websites is restricted, and controlled access to resources is possible using Cross-Origin Resource Sharing (CORS).

Cross-Origin Resource Sharing (CORS)

Understanding and Fixing CORS Error

CORS is implemented on the server-side; it cannot be reconfigured on the client-side. The CORS behavior, commonly termed as CORS error, is a mechanism to restrict users from accessing shared resources.

This is not an error but a security measure to secure users or the website which you are accessing from a potential security breach.

This breach may occur due to incomplete or improper HTTP headers on the client-side implementation (eg. missing authorization data such as API key).

Best Practices to Avoid CORS Errors

Let’s discuss some of the best practices for avoiding CORS errors by using a Custom Field Extension in Contentstack.

Proxy the API Request While Using External Calls in an Extension

Free Proxies can be great for testing, but relying on a free third-party tool is not advisable for something you will use on the production site. In such cases, a more stable solution is to call the API from a server and make the data available on the client-side.

Use a Serverless Function

1. Create a custom extension in Contentstack using the UI extension SDK. This extension will make an API call to the Google Maps API to fetch the data in your entry.
   The request will fail due to the cross-origin policy set at Google’s server, which will not let you fetch the data, resulting in a CORS error at your client-side.
2. To solve this problem, you can create an API Gateway URL in AWS with CORS enabled to serve the responses from the Google Maps API with our AWS Lambda function. For example:

    exports.handler = async (event) => {
   try{
   
       return {
         statusCode: 200,
         headers: {
           'Content-Type': 'application/json',
           'Access-Control-Allow-Headers':
             'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token',
           'Access-Control-Allow-Methods': 'OPTIONS,POST',
           'Access-Control-Allow-Credentials': true,
           'Access-Control-Allow-Origin': '*',
           'X-Requested-With': '*',
         },
         body: JSON stringified object,
       };
     } catch (error) {
       console.log(error);
       return {
         statusCode: 500,
         headers: {
           'Content-Type': 'application/json',
           'Access-Control-Allow-Headers':
             'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token',
           'Access-Control-Allow-Methods': 'OPTIONS,POST',
           'Access-Control-Allow-Credentials': true,
           'Access-Control-Allow-Origin': '*',
           'X-Requested-With': '*',
         },
         body: JSON.stringify({
           name: error.name,
           code: error.code,
           message: error.message,
         }),
       };
     }
   };
   

3. The extension that we have created will make an appropriate call i.e., GET, POST, and so on, to our API Gateway URL & trigger our lambda function.
4. The AWS Lambda will then return the maps API response to our client-side. This will fetch the maps data from Google Maps within your entry in Contentstack.

Note: For external hosting of the extension source code, the ‘allow-same-origin’ option will be enabled. Here, the origin refers to the domain where you’ve hosted the extensions. Also, ensure that the response header has the exact origin URL passed in the request header.
For Contentstack-hosted extensions, the iframe’s origin will be null as we don’t enable the ‘allow-same-origin’ flag.

CORS Issue in Frontend Frameworks

The CORS configuration can sometimes be tricky to achieve, and hence developers serve both the backend and frontend under the same domain in production.

To minimize this effort and provide flexibility to work with CORS, React, Nuxt, Express, etc. allow users to replicate the setup in development. This setup is done at the server end, so whenever a cross-origin request is made to the server, we can use a  middleware like http-proxy-middleware to proxy requests.

Furthermore, we can also redirect and change the path of the request by using options like pathRewrite.