Hibernate 动�?HQL

GhostZhang — Thu, 08 Sep 2011 03:02:00 GMT

在开发的时候，很多时候都遇到�q�需要动态拼写SQL�Q�有的是在配�|�文件中写SQL�Q�有的是在Java代码中拼写SQL�Q�以配置文�g拼SQL的可以拿IBatis��Z��表，但是很多时候是使用Hibernate的，�q�个时候就惌��是Hibernate能像IBatis那样写就好了�?/span>

�q�个时候就惛_��了模板语�a�和配�|�文件的�l�合。模板引擎可以选择Velocity�Q�简单而不失强大，配置文�g可以模仿Hibernate的sql-query 的XML文�g�?/span>

Sq-query的示例代码如�?SQL or HQL)�Q?br />

"http://www.anyframejava.org/dtd/anyframe-dynamic-hibernate-mapping-4.0.dtd">

                    SELECT  USER_ID,NAME
            FROM users_table Where 1=1
            #if($name && $name.length() > 1)
          AND name =:name
            #end
    ]]>


             FROM users
        Where 1=1
            #if($name && $name.length() > 1)
                AND name =:name
            #end
        ]]>

在系�l�加载时�Q�需要把配置文�g加蝲到系�l�中。加载代码关键部分如下：

1 public class DynamicHibernateImpl implements InitializingBean, ResourceLoaderAware, ApplicationContextAware

2 public void afterPropertiesSet() throws Exception {
3          for (int i = 0; i < fileNames.size(); i++) {
4             String fileName = ((String) fileNames.get(i)).trim();
5             if (resourceLoader instanceof ResourcePatternResolver) {
6                 try {
7                     Resource[] resources=((ResourcePatternResolver) resourceLoader).getResources(fileName);
8                   buildHQLMap(resources);
9                 } catch (IOException ex) {
10                     throw new Exception("Could not resolve sql definition resource pattern [" + fileName + "]", ex);
11                 }
12             } else {
13                 Resource resource = resourceLoader.getResource(fileName);
14                 buildHQLMap(new Resource[] { resource });
15             }
16         }
17     }
18  protected void buildHQLMap(Resource[] resources) throws Exception {
19         for (int i = 0; i < resources.length; i++) {
20             buildHQLMap(resources[i]);
21         }
22     }
23  private void buildHQLMap(Resource resource) throws Exception {
24         try {
25             InputSource inputSource = new InputSource(resource.getInputStream());
26             org.w3c.dom.Document doc = this.documentLoader.loadDocument(inputSource, null, null, org.springframework.util.xml.XmlValidationModeDetector.VALIDATION_NONE, false);
27             Element root = doc.getDocumentElement();
28             List querys = DomUtils.getChildElements(root);
29             for(Element query:querys){
30                 String queryName = query.getAttribute("name");
31                 if (StringUtils.isEmpty(queryName)) {
32                     throw new Exception("DynamicHibernate Service : name is essential attribute in a .");
33                 }
34                 if(statements.containsKey(queryName)){
35                     throw new Exception("DynamicHibernate Service : duplicated query in a ."+queryName);
36                 }
37                 statements.put(queryName, DomUtils.getTextValue(query));
38             }
39         } catch (SAXParseException se) {
40             throw se;
41         } catch (IOException ioe) {
42             throw ioe;
43         }
44     }

Spring的配�|�文件示例如下：

class="com.company.DynamicHibernateImpl">

classpath*:hibernate/dynamic/dynamic-hibernate-*.xml

下一步是在��用时调用sql�q�调用模板方法，�q�行sql动态化�?/span>

�q�是DynamicHibernateImpl�q�个�c?/span>

1   public List findList(String queryName, Map params, int pageIndex, int pageSize) throws Exception {
2         Context context = generateVelocityContext(params);
3         Query query = findInternal(queryName, context);
4         if (pageIndex > 0 && pageSize > 0) {
5             query.setFirstResult((pageIndex - 1) * pageSize);
6             query.setMaxResults(pageSize);
7         }
8       return query.list();
9     };
10   private Context generateVelocityContext(Map params) {
11         VelocityContext context = new VelocityContext();
12         if (null == params) {
13             return null;
14         }
15         Iterator iterator = params.keySet().iterator();
16         while (iterator.hasNext()) {
17             String key = iterator.next();
18             Object value = params.get(key);
19             if (null == value) {
20                 continue;
21             }
22             context.put(key, value);
23         }
24         return context;
25     };
26  private Query findInternal(String queryName, Context context) throws Exception {
27         String sql = findSQLByVelocity(queryName, context);
28         Query query = sessionFactory.getCurrentSession().createQuery(sql);
29         String[] namedParams = query.getNamedParameters();
30         setProperties(query, context, namedParams);
31         return query;
32     };
33  private String findSQLByVelocity(String queryName, Context context) throws Exception {
34         if (context == null)
35             context = new VelocityContext();
36         String sql = getSqlByName(queryName);
37         StringWriter writer = new StringWriter();
38         Velocity.evaluate(context, writer, "Hibernate", sql);
39         sql = writer.toString();
40         return sql;
41     };
42 protected String getSqlByName(String queryKey) {
43         return statements.get(queryKey);
44     }

��p��些�?/span>

大家也许有更好的�Ҏ��Q�欢�q�交��?/span>

QQ:24889356

GhostZhang 2011-09-08 11:02 发表评论

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Hibernate 动�?HQL