Spring

Prerequisite

RESTful web service

Get the POST request body from HttpServletRequest

req.getReader().lines().collect(Collectors.joining());

Spring cache

Cache with key on multiple arguments

@CachePut(value="cache_goods", key="{#codeName, #g.gid}")
public Goods updateGoods (String codeName, Goods g) {
    ...
}

Get value from native cache instance

AnnotationConfigApplicationContext appCtx = AppContext.getCacheAnnotContext();
SimpleCacheManager cacheMgr = (SimpleCacheManager) appctx.getBean("cacheMgr");
GuavaCache guc = (GuavaCache) cacheMgr.getCache("cache_company");
ConcurrentMap<Object, Object> map =  guc.getNativeCache().asMap();
String value = (String) map.get( Arrays.asList(token) );
Cache configuration with annotation
AppContext.java
public class AppContext {    
    private static AnnotationConfigApplicationContext _cache_annot_ctx = null;

    private AppContext() { }

    public static AnnotationConfigApplicationContext getCacheAnnotContext() {                
        synchronized (AppContext.class) {
            if (null == _cache_annot_ctx) {                    
                _cache_annot_ctx = new AnnotationConfigApplicationContext();
                    _cache_annot_ctx.register(CacheConfig.class);
                _cache_annot_ctx.refresh();                    
            }
        }        
        return _cache_annot_ctx;
    }
}
CacheConfig
@Configuration
@ComponentScan("org.venraas.hermes.apollo.*")
@EnableCaching
public class CacheConfig {

    @Bean(name="cacheMgr")
    public CacheManager cacheManager() {
        SimpleCacheManager cacheManager = new SimpleCacheManager();
        List<GuavaCache> cache_list = new ArrayList<GuavaCache>();

        GuavaCache cache_company = 
                    new GuavaCache(
                            "cache_company", 
                            CacheBuilder.newBuilder()
                            .maximumSize(Constant.CACHE_SIZE_10K)
                            .expireAfterWrite(30, TimeUnit.SECONDS)
                            .build());

        cache_list.add(cache_company);       
        cacheManager.setCaches(cache_list);
        return cacheManager;
  }
CompanyClient.java
package org.venraas.hermes.apollo.raas;
...
@Service
public class CompanyClient {
    @Cacheable(value="cache_company", key="{#token}")
    public String getCodeName(String token) {
        ...        
    }
}

@PropertySource - read the values from property file

  • application.properties

    conn.timeout=2000

  • Config.java

    public class Config {
  int conn_timeout;

  static Config _conf = new Config();    

  private Config() { }

  static public Config getInstance() {        
      return _conf;
  }

  public int getConn_timeout() {
      return conn_timeout;
  }

  public void setConn_timeout(int ms) {
      this.conn_timeout = ms;
  }
}

  • @PropertySource 

    @Configuration
@PropertySource("classpath:application.properties")
public class AppProperty {

  @Value("${conn.timeout}")
  private String conn_timeout;    

  @Autowired
  Environment env;

  /**
   * The Singleton instance creates as application startup automatically.   
   * @return Config the singleton instance
   */
  @Bean
  public Config getConfig() {
      Config cfg = Config.getInstance();
      cfg.setConn_timeout(Integer.valueOf(env.getProperty("conn.timeout")));        
      return cfg;
  }
}

  • Bean usage

    Config cfg = Config.getInstance()
int timout = cfg.getConn_timeout();

Spring Data - JPA and PostgresSQL

Quick Tips

Request parameters validation

Spring-starter-project- package war file

Converting a Spring Boot JAR Application to a WAR

Enabling Cross Origin Requests

@CrossOrigin
@RequestMapping("hello")
public Greeting sayHello(
        @RequestParam(value="name", required=false, defaultValue="Stranger") String name, 
        HttpServletResponse response) {

        //-- response body
    return new Greeting(counter.incrementAndGet(), String.format(template, name));
}

Understanding CORS

Customize dependency versions with Maven

Reference

RESTful

Cross-Origin Resource Sharing (CORS)

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