value-type<\/code>):<\/p>\n<config ...>\n\n <!-- Persistent cache directory -->\n ...\n <!-- Default cache template -->\n ...\n\n <!-- Cache configuration -->\n <cache alias=\"areaOfCircleCache\" uses-template=\"default\">\n <key-type>java.lang.Integer<\/key-type>\n <value-type>java.lang.Double<\/value-type>\n <\/cache>\n\n<\/config><\/pre>\nI would like to point out that we could have configured the cache without the cache template. All settings made in the cache-template<\/code> tag can also be used directly within the cache<\/code> tag.<\/p>\nNote<\/strong>: If the cache key consists of more than one method parameter, the type java.util.ArrayList<\/code> must be used as the key-type.<\/p>\n5.4.3 Wiring of ehcache.xml with application.properties<\/h4>\n
Finally, we tell the application.properties<\/code> file where our configuration file for Ehcache is located:<\/p>\nspring.cache.jcache.config=classpath:ehcache.xml<\/pre>\n5.5 Simple RestController<\/h3>\n
We now use our CalculationService<\/code> within the class CalculationRestController<\/code> and implement a simple REST endpoint, which gives us the result for the calculation of a circular area:<\/p>\n@RestController\n@RequestMapping(\"\/rest\/calculate\")\npublic class CalculationRestController {\n\n private final CalculationService calculationService;\n\n @Autowired\n public CalculationRestController(CalculationService calculationService) {\n this.calculationService = calculationService;\n }\n\n @GetMapping(path = \"\/areaOfCircle\", produces = MediaType.APPLICATION_JSON_VALUE)\n public ResponseEntity<Double> areaOfCircle(@RequestParam int radius) {\n double result = calculationService.areaOfCircle(radius);\n\n return ResponseEntity.ok(result);\n }\n\n}<\/pre>\nIf, for example, we call the URL http:\/\/localhost:8080\/rest\/calculate\/areaOfCircle?radius=6<\/code> after starting our application, the area of a circle with a radius of 6 is calculated and the result is displayed in the browser or in Postman.<\/p>\nFor the first call of the URL, the calculation of the circle area is still carried out. For all further calls, we get the result from the cache. Our built-in log output shows that the method is actually entered only once.<\/p>\n
If we calculate the circular area for a radius of 3, then the method is always executed, because the specified radius does not meet the cache condition #radius > 5<\/code>. A possible log output could be as follows (for a better overview I have omitted the output of the CacheLogger<\/code>):<\/p>\n2019-06-10 16:13:20.605 INFO (...) : calculate the area of a circle with a radius of 6\n2019-06-10 16:13:29.787 INFO (...) : calculate the area of a circle with a radius of 3\n2019-06-10 16:13:30.433 INFO (...) : calculate the area of a circle with a radius of 3\n2019-06-10 16:13:30.820 INFO (...) : calculate the area of a circle with a radius of 3\n2019-06-10 16:13:30.980 INFO (...) : calculate the area of a circle with a radius of 3\n2019-06-10 16:13:31.265 INFO (...) : calculate the area of a circle with a radius of 3<\/pre>\n6. Further examples<\/h2>\n6.1 Key Generator<\/h3>\n
If the possibilities of the SpEL for the generation of the cache key are not enough, the annotation @Cacheable<\/code> offers the possibility to use its own KeyGenerator<\/code> bean. The bean must implement the functional interface KeyGenerator<\/code>. The name of the bean must be specified as the value for the annotation parameter keyGenerator<\/code>:<\/p>\n@Cacheable(value = \"multiplyCache\", keyGenerator = \"multiplyKeyGenerator\")\npublic double multiply(int factor1, int factor2) {\n LOG.info(\"Multiply {} with {}\", factor1, factor2);\n return factor1 * factor2;\n}<\/pre>\nWe define the associated bean in the class EhcacheConfig<\/code>:<\/p>\n@Configuration\n@EnableCaching\npublic class EhcacheConfig {\n\n @Bean\n public KeyGenerator multiplyKeyGenerator() {\n return (Object target, Method method, Object... params) -> \n method.getName() + \"_\" + Arrays.toString(params);\n }\n\n}<\/pre>\n6.2 @CacheEvict<\/h3>\n
A cache can become very large very quickly. The problem with large caches is that they occupy a lot of important main memory and mostly consist of stale data that is no longer needed.<\/p>\n
To avoid inflated caches, you should, of course, have configured a meaningful eviction strategy. On the other hand, it is also possible to empty the cache based on requests. The following example shows how to remove all entries from the caches areaOfCircleCache<\/code> and multiplyCache<\/code>.<\/p>\n@CacheEvict(cacheNames = {\"areaOfCircleCache\", \"multiplyCache\"}, allEntries = true)\npublic void evictCache() {\n LOG.info(\"Evict all cache entries...\");\n}<\/pre>\n6.3 @CacheConfig<\/h3>\n
The @CacheConfig<\/code> annotation allows us to define certain cache configurations at the class level. This is especially useful if certain cache settings are the same for all methods to be cached:<\/p>\n@Service\n@CacheConfig(cacheNames = \"studentCache\")\npublic class StudentService {\n\n \/\/ ...\n\n @Cacheable\n public Optional<Student> find(Long id) {\n \/\/ ... \n }\n\n @CachePut(key = \"#result.id\")\n public Student create(String firstName, String lastName, String courseOfStudies) {\n \/\/ ...\n }\n\n}<\/pre>\nBoth the find()<\/code> and create()<\/code> methods use the studentCache<\/code> cache in this example.<\/p>\n6.4 @CachePut<\/h3>\n
In the previous chapter of this post, we got to know @Cacheable<\/code>. Methods annotated with @Cacheable<\/code> are not executed again if a value already exists in the cache for the cache key. If the value does not exist in the cache, then the method is executed and places its value in the cache.<\/p>\nNow there is also the use case that we always want the method to be executed and its result to be placed in the cache. This is done using the @CachePut<\/code> annotation, which has the same annotation parameters as @Cachable<\/code>.<\/p>\nA possible scenario for using @CachePut<\/code> is, for example, creating an entity object, as the following example shows:<\/p>\n@CachePut(cacheNames = \"studentCache\", key = \"#result.id\")\npublic Student create(String firstName, String lastName, String courseOfStudies) {\n LOG.info(\"Creating student with firstName={}, lastName={} and courseOfStudies={}\", \n firstName, lastName, courseOfStudies);\n \n long newId = ID_CREATOR.incrementAndGet();\n Student newStudent = new Student(newId, firstName, lastName, courseOfStudies); \n \n \/\/ persist in database\n\n return newStudent;\n}<\/pre>\nThe key #result<\/code> is a placeholder provided by Spring and refers to the return value of the method. The ID of the student is, therefore, the cache key. The cache entry is the return value of the method, the student in our example.<\/p>\nThe method now creates a student object and stores it in the studentCache<\/code> at the end. The next time this object is requested, it can be retrieved directly from the cache.<\/p>\n7. JSR 107 Annotations vs. Spring Cache Annotations<\/h2>\n
Since Ehcache is fully JSR 107 compliant, JSR 107 annotations can be used instead of Spring Cache annotations. Spring recommends to choose one side and not to mix the annotations at all. The following table shows a comparison of the available cache annotations:<\/p>\n
\n\n\nJSR 107 \/ JCache Annotations<\/strong><\/td>\nSpring Cache Annotations<\/strong><\/td>\n<\/tr>\n\n@CacheResult<\/code><\/td>\n@Cacheable<\/code><\/td>\n<\/tr>\n\n@CacheRemove<\/code><\/td>\n@CacheEvict<\/code><\/td>\n<\/tr>\n\n@CacheRemoveAll<\/code><\/td>\n@CacheEvict(allEntries=true)<\/code><\/td>\n<\/tr>\n\n@CachePut<\/code><\/td>\n@CachePut<\/code><\/td>\n<\/tr>\n\n@CacheDefaults<\/code><\/td>\n@CacheConfig<\/code><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n8. Summary<\/h2>\nIn this blog post, we looked at how to configure and use the cache provider Ehcache in Spring Boot. We looked at the following:<\/p>\n \n- \n
\n- What are caches and what are they good for?<\/li>\n
- How does caching work in Spring?<\/li>\n
- Using Spring Cache Annotations\n
\n@EnableCaching<\/code><\/li>\n@Cacheable<\/code><\/li>\n@CacheEvict<\/code><\/li>\n@CachePut<\/code><\/li>\n@CacheConfig<\/code><\/li>\n<\/ul>\n<\/li>\n- Configuration of Ehcache caches<\/li>\n
- Custom cache keys<\/li>\n
- Comparison JSR 107 Annotations and Spring Cache Annotations<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
Also, like to check out the project repository at GitHub<\/a>. It contains a fully functional Spring Boot application with Ehcache as the cache provider.<\/p>\n","protected":false},"excerpt":{"rendered":"1. Introduction In today’s blog post we will look at how we can use the caching provider Ehcache in Spring Boot. Ehcache is an open source library implemented in Java for implementing caches in Java programs, especially local and distributed caches in main memory or on the hard disk. Thanks to the implementation of JSR-107, […]Continue reading<\/a><\/p>\n","protected":false},"author":117,"featured_media":4575,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_lmt_disableupdate":"","_lmt_disable":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false},"version":2}},"categories":[104],"tags":[236,237,29],"class_list":["post-5513","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-spring-boot","tag-cache","tag-ehcache","tag-spring-boot"],"jetpack_publicize_connections":[],"aioseo_notices":[],"modified_by":"jt","jetpack_sharing_enabled":true,"jetpack_featured_media_url":"https:\/\/springframework.guru\/wp-content\/uploads\/2018\/06\/NewBannerBOOTSWeb.jpg","jetpack_shortlink":"https:\/\/wp.me\/p5BZrZ-1qV","_links":{"self":[{"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/posts\/5513"}],"collection":[{"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/users\/117"}],"replies":[{"embeddable":true,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/comments?post=5513"}],"version-history":[{"count":11,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/posts\/5513\/revisions"}],"predecessor-version":[{"id":8287,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/posts\/5513\/revisions\/8287"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/media\/4575"}],"wp:attachment":[{"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/media?parent=5513"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/categories?post=5513"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/tags?post=5513"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} | | | | | | | | | | | |