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/*
JPA (Java Persistence API)

Transaction Management with an Entity-Mananger:
---
entityManager.getTransaction().begin();
entityManager.persist(<some-entity>);
entityManager.getTransaction().commit();
entityManager.clear();

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-- Set a Sequence to a specific value
select setval('address_seq', 1, true);

-- Show last used sequence value
SELECT last_value FROM my_sequence_name;

-- Show text from a TEXT datatype column: http://www.solewing.org/blog/2015/08/hibernate-postgresql-and-lob-string/
SELECT
  convert_from(loread(
    lo_open(my_large_text::int, x'40000'::int), x'40000'::int), 'UTF-8'

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# Start psql
> psql

<current-database>=#

# Exit psql
\q

# Show all tables
\dt

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// Enable component-scanning and auto-configuration with @SpringBootApplication Annotation
// It combines @Configuration + @ComponentScan + @EnableAutoConfiguration
@SpringBootApplication
public class FooApplication {
  public static void main(String[] args) {
    // Bootstrap the application
    SpringApplication.run(FooApplication.class, args);
  }
}

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Glossar

• Sidecar - Process that encapsulates required technologies (e.g. logging, monitoring, service discovery, etc.) in the microservices environment and makes them available to microservices that are not able to use those technologies natively
• Immutable Server -

Configuration + Coordination

• Zookeeper - https://zookeeper.apache.org/ - Provides configs in a hierarchical key-value store that is replicated and synchronized across large distributed systems.
• etcd - https://github.com/coreos/etcd - Like Zookeeper. Distributed reliable key-value store for the most critical data of a distributed system. Provides a REST API. It is possible to do locking in a distributed system with it.
• Spring Cloud Config - Provides a REST API. Config files can be based in a Git repo. The config data can be encrypted (e.g. for passwords in config files)

Service Discovery

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// Switch Colour Representation (HEX -> HSL -> ...)
Shift + Click on the colourpicker

// Search DOM-Nodes by CSS classnames
Cmd + F -> ".hidden p"

// Jump to a specific line
Cmd + P -> ":39"

// Open a File by searching for the filename

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// imports a couple of java tasks
apply plugin: "java"

// List available tasks in the shell
> gradle tasks

// A Closure that configures the sourceSets Task
// Sets the main folder as Source folder (where the compiler is looking up the .java files)
sourceSets {
  main.java.srcDir "src/main"

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# Create a file and insert some text with the ">" operator
echo "my new site" > index.html

# Show PATH
echo $PATH # /usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

# /usr/local/bin is in the PATH by default

# Create symbolic link (symlink)
ln -s "/Applications/Sublime Text.app/Contents/SharedSupport/bin/subl" /usr/local/bin/sublime

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// Show rendered HTML
const wrapper = shallow(<App />)
console.log(wrapper.debug())

// Disable lifecycle methods of react within tests
const wrapper = mount(<App />, { disableLifecycleMethods: true })

// Assert number of occurrences
expect(wrapper.find('p').length).toBe(1)

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// Return JSON without Jackson mapping classes
@RequestMapping("/users") 
public @ResponseBody Map<String, String> getUsers () {
    
  Map<String, String> map = new HashMap<String, String>();
  map.put("user", "Clark Kent");
    
  return map;
}