SpringMvc 系统启动时加载数据到内存中

转：http://blog.csdn.net/newstruts/article/details/18668269

 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

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

// @PostConstruct
public void init(ServletContext sc) {
this.sc = sc;
List<Dictionary> 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<String, Map<String, String>> localDics = new HashMap<String, Map<String, String>>();
Map<String, String> 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<String, String>();
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<String, String> findDictionary(String type) {
JSONObject jsonObject = (JSONObject) sc.getAttribute(type);
return jsonObject;
}
}