获得hibernate的sql语句(2.1.6)
类别: JAVA教程 
获得hibernate的sql语句我们知道hibernate会将hql解析成sql，也许在某些时候，我们需要这些sql。不过hibernate的接口中没有公开的api，看来我们得自己行动了。1.开始前的工作 1.1 知道如何阅读javadoc api 1.2 知道如何使用ant编译hibernate源码包 1.3 hibernate源码包在hibernate压缩包的src目录,api文档在doc目录2.在执行Query.list()方法时，hibernate在控制台输出sql。从api文档中我们知道， Query接口有个实现类是net.sf.hibernate.impl.AbstractQueryImpl，但这个虚类中并没有实现list方法，继续查该类的子类net.sf.hibernate.impl.QueryImpl，呵呵，找到了。 list
public List list() throws HibernateException
Description copied from interface: Query Return the query results as a List. If the query contains multiple results pre row, the results are returned in an instance of Object[].
Returns: the result list Throws: HibernateException3.查看net.sf.hibernate.impl.QueryImpl源代码，发现这里吧实现丢给了Session接口，看来我们得去找Session接口的麻烦。 public List list() throws HibernateException { verifyParameters(); Map namedParams = getNamedParams(); return getSession().find( bindParameterLists(namedParams), getQueryParameters(namedParams) );}4.接口是没有实现代码的，因此我们直接看实现类net.sf.hibernate.impl.SessionImple的源代码 public List find(String query, QueryParameters queryParameters) throws HibernateException {
if ( log.isTraceEnabled() ) { log.trace( "find: " + query ); queryParameters.traceParameters(factory); }
queryParameters.validateParameters();
QueryTranslator[] q = getQueries(query, false);
List results = Collections.EMPTY_LIST;
dontFlushFromFind++; //stops flush being called multiple times if this method is recursively called
//execute the queries and return all result lists as a single list try { for ( int i=0; i<q.length; i++ ) { List currentResults; try { currentResults = q[i].list(this, queryParameters); // 原来list是由这个类做的 } catch (SQLException sqle) { throw new JDBCException("Could not execute query", sqle); } currentResults.addAll(results); results = currentResults; } } finally { dontFlushFromFind--; } return results;}
5. 在api文档左下角All Classes框架搜索QueryTranslator，查到后点击查看api，嗯，有料。 getSQLString
public String getSQLString()
Description copied from class: Loader The SQL query string to be called; implemented by all subclasses
Specified by: getSQLString in class Loader6.但是我们并不想处理第4步中找到的find方法的QueryParameters参数，怎么办捏？参考一下其他find方法 private static final Object[] NO_ARGS = ArrayHelper.EMPTY_STRING_ARRAY;private static final Type[] NO_TYPES = ArrayHelper.EMPTY_TYPE_ARRAY;
/*** Retrieve a list of persistent objects using a hibernate query*/public List find(String query) throws HibernateException { return find(query, NO_ARGS, NO_TYPES); // 他交给了三个参数的接口 }
public List find(String query, Object value, Type type) throws HibernateException { return find( query, new Object[] { value }, new Type[] { type } ); // 又丢给另一个接口处理 }
public List find(String query, Object[] values, Type[] types) throws HibernateException { return find(query, new QueryParameters(types, values) ); // 回到2参数的接口手里了 :) }
7.开始修改，将第4步找到的代码复制出来更改如下，然后添加回SessionImpl类 public String[] getSQLStrings(String query) throws HibernateException { // 采用单参数接口处理queryParameters的方法 QueryParameters queryParameters = new QueryParameters(NO_ARGS, NO_TYPES); if ( log.isTraceEnabled() ) { log.trace( "find: " + query ); queryParameters.traceParameters(factory); }
queryParameters.validateParameters();
QueryTranslator[] q = getQueries(query, false);
String[] results = new String[q.length]; // 创建返回值
dontFlushFromFind++; //stops flush being called multiple times if this method is recursively called
//execute the queries and return all result lists as a single list try { for ( int i=0; i<q.length; i++ ) { try { results[i] = q[i].getSQLString(); // 获得sql语句 :) } catch (SQLException sqle) { throw new JDBCException("Could not execute query", sqle); } } } finally { dontFlushFromFind--; } return results;}
8.给Session接口增加一个方法 public String[] getSQLStrings(String query) throws HibernateException;9.编译之后大功告成，我们可以使用Session.getSQLStrings(query)获得sql语句数组 :)
