/**
* 根据数据库方言，生成特定的分页sql
*
* @param sql
* @param page
* @return
*/
private String generatePageSql(String sql, Page page) {
if (page != null && Tools.notEmpty(dialect)) {
StringBuffer pageSql = new StringBuffer();
if ("mysql".equals(dialect)) {
pageSql.append(sql);
pageSql.append(" limit " + page.getCurrentResult() + "," + page.getShowCount());
} else if ("oracle".equals(dialect)) {
pageSql.append("select * from (select tmp_tb.*,ROWNUM row_id from (");
pageSql.append(sql);
// pageSql.append(") as tmp_tb where ROWNUM<=");
pageSql.append(") tmp_tb where ROWNUM<=");
pageSql.append(page.getCurrentResult() + page.getShowCount());
pageSql.append(") where row_id>");
pageSql.append(page.getCurrentResult());
}
return pageSql.toString();
} else {
return sql;
}
}
public Object intercept(Invocation ivk) throws Throwable {
// TODO Auto-generated method stub
if (ivk.getTarget() instanceof RoutingStatementHandler) {
RoutingStatementHandler statementHandler = (RoutingStatementHandler) ivk.getTarget();
BaseStatementHandler delegate =
(BaseStatementHandler) ReflectHelper.getValueByFieldName(statementHandler, "delegate");
MappedStatement mappedStatement =
(MappedStatement) ReflectHelper.getValueByFieldName(delegate, "mappedStatement");
if (mappedStatement.getId().matches(pageSqlId)) { // 拦截需要分页的SQL
BoundSql boundSql = delegate.getBoundSql();
Object parameterObject =
boundSql
.getParameterObject(); // 分页SQL<select>中parameterType属性对应的实体参数，即Mapper接口中执行分页方法的参数,该参数不得为空
if (parameterObject == null) {
throw new NullPointerException("parameterObject尚未实例化！");
} else {
Connection connection = (Connection) ivk.getArgs()[0];
String sql = boundSql.getSql();
// String countSql = "select count(0) from (" + sql+ ") as tmp_count"; //记录统计
String countSql =
"select count(0) from ("
+ sql
+ ") tmp_count"; // 记录统计 == oracle 加 as 报错(SQL command not properly ended)
PreparedStatement countStmt = connection.prepareStatement(countSql);
BoundSql countBS =
new BoundSql(
mappedStatement.getConfiguration(),
countSql,
boundSql.getParameterMappings(),
parameterObject);
setParameters(countStmt, mappedStatement, countBS, parameterObject);
ResultSet rs = countStmt.executeQuery();
int count = 0;
if (rs.next()) {
count = rs.getInt(1);
}
rs.close();
countStmt.close();
// System.out.println(count);
Page page = null;
if (parameterObject instanceof Page) { // 参数就是Page实体
page = (Page) parameterObject;
page.setEntityOrField(true);
page.setTotalResult(count);
} else { // 参数为某个实体，该实体拥有Page属性
Field pageField = ReflectHelper.getFieldByFieldName(parameterObject, "page");
if (pageField != null) {
page = (Page) ReflectHelper.getValueByFieldName(parameterObject, "page");
if (page == null) page = new Page();
page.setEntityOrField(false);
page.setTotalResult(count);
ReflectHelper.setValueByFieldName(parameterObject, "page", page); // 通过反射，对实体对象设置分页对象
} else {
throw new NoSuchFieldException(parameterObject.getClass().getName() + "不存在 page 属性！");
}
}
String pageSql = generatePageSql(sql, page);
ReflectHelper.setValueByFieldName(boundSql, "sql", pageSql); // 将分页sql语句反射回BoundSql.
}
}
}
return ivk.proceed();
}