本文以 Spring Boot 应用、MySQL 数据库为例。

新建 DictionaryService.java、DictionaryServiceImpl.java，新增借口方法：addDictionaryToServletContext，用于调用加载字典到内存。

/**
 * @author godcheese
 */
@Service
public class DictionaryServiceImpl implements DictionaryService {
   
    @Autowired
    private DictionaryMapper dictionaryMapper;

    @Autowired
    private WebApplicationContext webApplicationContext;

    private static final Logger LOGGER = LoggerFactory.getLogger(DictionaryServiceImpl.class);

    @Override
    public void addDictionaryToServletContext() {
        ServletContext servletContext = webApplicationContext.getServletContext();
        if (servletContext != null) {

            List<DictionaryEntity> dictionaryEntityList = dictionaryMapper.listAll();
            for (DictionaryEntity dictionaryEntity : dictionaryEntityList) {
                servletContext.setAttribute(dictionaryEntity.getKey().toUpperCase() + "." + dictionaryEntity.getValueSlug().toUpperCase(), dictionaryEntity.getValue());
            }

            Map<String, List<DictionaryEntity>> dictionaryEntityMap = new HashMap<>(6);
            for (DictionaryEntity dictionaryEntity : dictionaryEntityList) {
                String key = dictionaryEntity.getKey().toUpperCase();
                if (dictionaryEntityMap.containsKey(key)) {
                    List<DictionaryEntity> dictionaryEntityList1 = dictionaryEntityMap.get(key);
                    if (!dictionaryEntityList1.contains(dictionaryEntity)) {
                        dictionaryEntityList1.add(dictionaryEntity);
                        dictionaryEntityMap.put(key, dictionaryEntityList1);
                    }
                } else {
                    List<DictionaryEntity> dictionaryEntityList2 = new ArrayList<>(1);
                    dictionaryEntityList2.add(dictionaryEntity);
                    dictionaryEntityMap.put(key, dictionaryEntityList2);
                }
            }

            for (Map.Entry entry : dictionaryEntityMap.entrySet()) {
                servletContext.setAttribute((String) entry.getKey(), entry.getValue());
            }

        }
    }
}

新建 ApplicationStartupRunner.java，用于程序启动时进行的操作，此处调用 DictionaryService 的 addDictionaryToServletContext 方法，执行将字典加载到内存。

/**
 * @author godcheese
 * @date 2018/2/22 16:19
 */
@Component
@Order
public class ApplicationStartupRunner implements CommandLineRunner {

    private static final Logger LOGGER = LoggerFactory.getLogger(ApplicationStartupRunner.class);

    @Autowired
    private DictionaryService dictionaryService;

    @Override
    public void run(String... strings) throws Exception {

        // 首次启动加载数据字典到 ServletContext 内存
        dictionaryService.addDictionaryToServletContext();

    }
}