/freeMarkerAndGirdFS

How to use freemarker and mongoDb GridFs

Primary LanguageJava

FreeMarker技术总结

初始数据

map.put("name","hsiang sun");
map.put("list",friendsList);
map.put("stumap",map2);

空值处理方式

${(stuMap[stu1].name)!''} <!--如果为空就返回空子串-->

插值表达式

Hello ${name}

List遍历

<#list list as stu>
    <tr>
        <td>${stu.name}</td>
        <td>${stu.age}</td>
        <#-- <td>${stu.birthday}</td>-->
		<td>${stu.money}</td>
	</tr>
</#list>

Map遍历

<!--Method one-->
<p>The name of  Student 1:<span>${stumap['stu1'].name}</span></p>
<!--Method two-->
<p>The age of  Student 2:<span>${stumap.stu2.age}</span></p>
<!--Method three-->
 <#list  stumap?keys as object>
     ${stumap[object].name}
 </#list>

逻辑运算

运算符 表达式
> gt
>= gte
< lt
<= lte

内建函数

  • 集合大小：${集合名?size}
  • 日期格式化：
含义 表达式
显示年月日 ${today?date}
显示时分秒 ${today?time}
显示日期+时间 ${today?datetime}
自定义格式化时间 ${today?string("yyyy年MM月")}
  • 数字转成字串：${num?c} 123,145,233 =>123145233
  • JSON转Object
<#assign text="{'back':'ICBC','account':'121464657'}" />
<#assign data=text?eval />
${data.bank} ${data.account}

GridFS

由MongeDB开发，将大于256KB的数据分段存入fs.chunks集合中。其本身索引保存在fs.files集合中。

导入依赖

<dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-mongodb</artifactId>
    <version>2.0.11.RELEASE</version>
</dependency>

存储数据(将文件以二进制形式存储)

File file =new File("C:\\Users\\xy110\\Pictures\\girl00.jpg");
FileInputStream ins = null;
try {
    ins = new FileInputStream(file);
} catch (FileNotFoundException e) {
    e.printStackTrace();
}
ObjectId objectId = gridFsTemplate.store(ins, "girl");

获取数据

  • 首先注入GridFSBucket 对象

    @Configuration
public class MongodbConfig {
    private String db="xc_cms";//数据库名实际情况应该从application.yml中获取
    @Bean
    public GridFSBucket createGridFsBucket(MongoClient mongoClient){
        MongoDatabase database = mongoClient.getDatabase(db);
        GridFSBucket gridFSBucket = GridFSBuckets.create(database);
        return gridFSBucket;
    }
}

  • 获取流并写入数据

     //根据ObjectId查询
        GridFSFile gridFSFile = gridFsTemplate.findOne(Query.query(Criteria.where("_id").is("5d3acd3fec28a022bc747336")));
        //建立一个下载流
        GridFSDownloadStream gridFSDownloadStream = gridFSBucket.openDownloadStream(gridFSFile.getObjectId());
        //获取流
        GridFsResource gridFsResource = new GridFsResource(gridFSFile,gridFSDownloadStream);
        InputStream inputStream = gridFsResource.getInputStream();
        File outFile = new File("C:\\Users\\xy110\\Desktop\\mogo.jpg");
        byte[] buff =new byte[1024];
        int len = 0;
        OutputStream ous = new FileOutputStream(outFile);
        while ( (len= inputStream.read(buff)) != -1 ){
            ous.write(buff,0,len);
        }
        ous.close();
        inputStream.close();