public StringBuilder buildPageSqlForMysql(String sql, PageParameter page) {
StringBuilder pageSql = new StringBuilder(100);
pageSql.append(sql);
pageSql.append(" limit " + page.getOffset() + "," + page.getLimit());
return pageSql;
}
public StringBuilder buildPageSqlForOracle(String sql, PageParameter page) {
StringBuilder pageSql = new StringBuilder(100);
String beginrow = String.valueOf((page.getCurrentPage() - 1) * page.getPageSize());
String endrow = String.valueOf(page.getCurrentPage() * page.getPageSize());
pageSql.append("select * from ( select temp.*, rownum row_id from ( ");
pageSql.append(sql);
pageSql.append(" ) temp where rownum <= ").append(endrow);
pageSql.append(") where row_id > ").append(beginrow);
return pageSql;
}
/**
* 从数据库里查询总的记录数并计算总页数，回写进分页参数<code>PageParameter</code>,这样调用 者就可用通过 分页参数 <code>PageParameter
* </code>获得相关信息。
*
* @param sql
* @param connection
* @param mappedStatement
* @param boundSql
* @param page
*/
private void setPageParameter(
String sql,
Connection connection,
MappedStatement mappedStatement,
BoundSql boundSql,
PageParameter page) {
// 记录总记录数
String countSql = "select count(0) as total from (" + sql + ") tt";
PreparedStatement countStmt = null;
ResultSet rs = null;
try {
countStmt = connection.prepareStatement(countSql);
setParameters(countStmt, mappedStatement, boundSql);
rs = countStmt.executeQuery();
int totalCount = 0;
if (rs.next()) {
totalCount = rs.getInt(1);
}
page.setTotalElements(totalCount);
// int totalPage = totalCount / page.getPageSize() + ((totalCount % page.getPageSize() == 0)
// ? 0 : 1);
// page.setTotalPage(totalPage);
} catch (SQLException e) {
logger.error("Ignore this exception", e);
} finally {
try {
rs.close();
} catch (SQLException e) {
logger.error("Ignore this exception", e);
}
try {
countStmt.close();
} catch (SQLException e) {
logger.error("Ignore this exception", e);
}
}
}
@Override
public Object intercept(Invocation invocation) throws Throwable {
StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
MetaObject metaStatementHandler =
MetaObject.forObject(
statementHandler,
DEFAULT_OBJECT_FACTORY,
DEFAULT_OBJECT_WRAPPER_FACTORY,
DEFAULT_REFLECTOR_FACTORY);
// 分离代理对象链(由于目标类可能被多个拦截器拦截，从而形成多次代理，通过下面的两次循环
// 可以分离出最原始的的目标类)
while (metaStatementHandler.hasGetter("h")) {
Object object = metaStatementHandler.getValue("h");
metaStatementHandler =
MetaObject.forObject(
object,
DEFAULT_OBJECT_FACTORY,
DEFAULT_OBJECT_WRAPPER_FACTORY,
DEFAULT_REFLECTOR_FACTORY);
}
// 分离最后一个代理对象的目标类
while (metaStatementHandler.hasGetter("target")) {
Object object = metaStatementHandler.getValue("target");
metaStatementHandler =
MetaObject.forObject(
object,
DEFAULT_OBJECT_FACTORY,
DEFAULT_OBJECT_WRAPPER_FACTORY,
DEFAULT_REFLECTOR_FACTORY);
}
if (null == dialect || "".equals(dialect)) {
logger.warn("Property dialect is not setted,use default 'mysql' ");
dialect = defaultDialect;
}
if (null == pageSqlId || "".equals(pageSqlId)) {
logger.warn("Property pageSqlId is not setted,use default '.*Page$' ");
pageSqlId = defaultPageSqlId;
}
MappedStatement mappedStatement =
(MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement");
PageParameter page = null;
Object type = metaStatementHandler.getValue("delegate.boundSql.parameterObject");
if (PageParameter.class.isInstance(type)) {
page = (PageParameter) type;
}
// 只重写需要分页的sql语句。通过MappedStatement的ID匹配，默认重写以Page结尾的
// MappedStatement的sql
if (mappedStatement.getId().matches(pageSqlId) && page != null && page.getLimit() > 0) {
BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql");
Object parameterObject = boundSql.getParameterObject();
if (parameterObject == null) {
throw new NullPointerException("parameterObject is null!");
} else {
// 分页参数作为参数对象parameterObject的一个属性
String sql = boundSql.getSql();
// 重写sql
String pageSql = buildPageSql(sql, page, dialect);
metaStatementHandler.setValue("delegate.boundSql.sql", pageSql);
// 采用物理分页后，就不需要mybatis的内存分页了，所以重置下面的两个参数
metaStatementHandler.setValue("delegate.rowBounds.offset", RowBounds.NO_ROW_OFFSET);
metaStatementHandler.setValue("delegate.rowBounds.limit", RowBounds.NO_ROW_LIMIT);
Connection connection = (Connection) invocation.getArgs()[0];
// 重设分页参数里的总页数等
setPageParameter(sql, connection, mappedStatement, boundSql, page);
}
}
// 将执行权交给下一个拦截器
return invocation.proceed();
}