Mybatis 在dao中获取分页的总记录数

萨尔法保护

/**
* get total count
* @param sqlSession
* @param statementName
* @param values
* @return
*/
private long getTotalCount(SqlSession sqlSession, String statementName,Object values ) {
Map parameterMap=toParameterMap(values);
long count=0l;
try {
MappedStatement mst = sqlSession.getConfiguration().getMappedStatement(statementName);
BoundSql boundSql = mst.getBoundSql(parameterMap);
String sql = " select count(*) total_count from (" + boundSql.getSql()+ ") ";
PreparedStatement pstmt = sqlSession.getConnection().prepareStatement(sql);
//BoundSql countBS = new BoundSql(mst.getConfiguration(),sql,boundSql.getParameterMappings(),parameterMap);  
setParameters(pstmt,mst,boundSql,parameterMap);
ResultSet rs=pstmt.executeQuery();
if (rs.next()){
count = rs.getLong("total_count");
}
rs.close();
pstmt.close();
} catch (Exception e) {
count=0l;
e.printStackTrace();
throw new RuntimeException(e);
}
return count;
}
/**
* 对SQL参数(?)设值,参考org.apache.ibatis.executor.parameter.DefaultParameterHandler
* @param ps
* @param mappedStatement
* @param boundSql
* @param parameterObject
* @throws SQLException
*/  
private void setParameters(PreparedStatement ps,MappedStatement mappedStatement,BoundSql boundSql,Object parameterObject) throws SQLException {  
ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());  
List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();  
if (parameterMappings != null) {
Configuration configuration = mappedStatement.getConfiguration();  
TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();  
MetaObject metaObject = parameterObject == null ? null: configuration.newMetaObject(parameterObject);  
for (int i = 0; i < parameterMappings.size(); i++) {  
ParameterMapping parameterMapping = parameterMappings.get(i);  
if (parameterMapping.getMode() != ParameterMode.OUT) {  
Object value;
String propertyName = parameterMapping.getProperty();  
PropertyTokenizer prop = new PropertyTokenizer(propertyName);
if (parameterObject == null) {  
value = null;  
} else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {  
value = parameterObject;  
} else if (boundSql.hasAdditionalParameter(propertyName)) {  
value = boundSql.getAdditionalParameter(propertyName);  
} else if (propertyName.startsWith(ForEachSqlNode.ITEM_PREFIX)&& boundSql.hasAdditionalParameter(prop.getName())) {  
value = boundSql.getAdditionalParameter(prop.getName());  
if (value != null) {  
value = configuration.newMetaObject(value).getValue(propertyName.substring(prop.getName().length()));  
}  
} else {  
value = metaObject == null ? null : metaObject.getValue(propertyName);  
}  
TypeHandler typeHandler = parameterMapping.getTypeHandler();  
if (typeHandler == null) {  
throw new ExecutorException("There was no TypeHandler found for parameter "+ propertyName + " of statement "+ mappedStatement.getId());  
}
typeHandler.setParameter(ps, i + 1, value, parameterMapping.getJdbcType());  
}  
}  
}  
}  
protected Map toParameterMap(Object parameter) {
if (parameter == null) {
return new HashMap();
}
if (parameter instanceof Map) {
return (Map<?,?>) parameter;
} else {
try {
return PropertyUtils.describe(parameter);
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}