SpringMvc 系统启动时加载数据到内存中

 在项目启动时加载数据到内存中(我这里是数据字典)，以后再代码中就不用每次从数据库去查询了

  Dictionary 数据字典实体 

  

package com.wonders.framework.dictionary.entity.po;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

import org.hibernate.annotations.GenericGenerator;

@Entity
@Table(name = "WC_DICTIONARY",schema="WST")
public class Dictionary {
	private String id;

        //key值
	private String key;

        //value值
	private String value;

        //数据字典类型
	private String type;
	
	@Id
	@GenericGenerator(name="idGenerator", strategy="uuid") //这个是hibernate的注解
	@GeneratedValue(generator="idGenerator")
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}

	@Column(name = "KEY", nullable = true, length = 50)
	public String getKey() {
		return key;
	}
	public void setKey(String key) {
		this.key = key;
	}

	@Column(name = "VALUE", nullable = true,  length = 50)
	public String getValue() {
		return value;
	}
	public void setValue(String value) {
		this.value = value;
	}

	@Column(name = "TYPE", nullable = true)
	public String getType() {
		return type;
	}
	public void setType(String type) {
		this.type = type;
	}
	

}

        

     SysInitBean  要初始化的Bean

     要实现  ServletContextAware 接口

         

package com.wonders.framework.base;

import java.util.Properties;

import javax.servlet.ServletContext;

import net.sf.json.JSONObject;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.context.ServletContextAware;

import com.wonders.framework.dictionary.service.DictionaryService;
import com.wonders.framework.util.FileUtil;

//实现ServletContextAware，可以获得servletcontext
//@Component注解了，直接在xml里配置这个bean就行了，系统自动调用
@Component
public class SysInitBean implements  ServletContextAware {
	@Autowired
	private DictionaryService dictionaryService;
	
	@Override
	public void setServletContext(ServletContext sc) {
		// 把项目名称放到application中
		String ctxPath=sc.getContextPath();
		sc.setAttribute("ctxPath",ctxPath);
		
		//初始化数据字典到application中
		dictionaryService.init(sc);
	}
}

DictionaryServiceImpl 

     用来查询数据字典

        

package com.wonders.framework.dictionary.service.impl;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;

import javax.servlet.ServletContext;

import net.sf.json.JSONObject;

import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.wonders.framework.dictionary.dao.DictionaryDao;
import com.wonders.framework.dictionary.entity.po.Dictionary;
import com.wonders.framework.dictionary.service.DictionaryService;
import com.wonders.framework.util.FileUtil;

@Component("dictionaryServiceImpl")
public class DictionaryServiceImpl implements DictionaryService {
	private static Logger logger = Logger.getLogger(DictionaryServiceImpl.class
			.getName());

	// private static Map> localDics = new
	// HashMap>();
	@Autowired
	private DictionaryDao dictionaryDao;
	private ServletContext sc;

	// @PostConstruct
	public void init(ServletContext sc) {
		this.sc = sc;
		List list = null;
		try {
			list = dictionaryDao.findAll();
		} catch (Exception e) {
			logger.error("数据字典数据查找失败!");
		}
		if (null == list) {
			return;
		}
		Map> localDics = new HashMap>();
		Map map = null;
		for (Dictionary dic : list) {
			String type = dic.getType();
			if (localDics.containsKey(type)) {
				map = localDics.get(type);
				map.put(dic.getKey(), dic.getValue());
			} else {
				map = new HashMap();
				map.put(dic.getKey(), dic.getValue());
				localDics.put(type, map);
			}
		}
		Properties prop = FileUtil
				.getProperties("/config/dictionary.properties");
		for (Object key : prop.keySet()) {
			Object value = prop.get(key);
			sc.setAttribute((String) key,
					JSONObject.fromObject(localDics.get(value)));
		}
	}

	public String getValue(String type, String key) {
		JSONObject jsonObject = (JSONObject) sc.getAttribute(type);
		return (String) jsonObject.get(key);
	}

	public boolean isDic(String type) {
		JSONObject jsonObject = (JSONObject) sc.getAttribute(type);
		return jsonObject == null ? false : true;
	}

	public String getKey(String type, String value) {
		JSONObject jsonObject = (JSONObject) sc.getAttribute(type);
		for (Object key : jsonObject.keySet()) {
			String sValue = (String) jsonObject.get(key);
			if (sValue.equals(value)) {
				return (String) key;
			}
		}
		return null;
	}

	// @PreDestroy
	// public void destroy() {
	// localDics = null;
	// }

	@SuppressWarnings("unchecked")
	public Map findDictionary(String type) {
		JSONObject jsonObject = (JSONObject) sc.getAttribute(type);
		return jsonObject;
	}
}

 在js中就可以用el表达式直接获取如： '${dicCategory}'

 在java代码中可以这样获取( String getValue(String type,String key);)

    type代表数据字典类型（如 区县）

   key （01）

  value (黄浦区)

    dis = dictionaryService.getValue("1", ‘01’);

   返回  汉字  黄浦区