/**
* 生成特定数据库的分页语句
*
* @param sql
* @param page
* @return
*/
private String buildPageSql(String sql, Page<?> page) {
if (page == null || dialect == null || dialect.equals("")) {
return sql;
}
StringBuilder sb = new StringBuilder();
int startRow = page.getOffset();
if ("mysql".equals(dialect)) {
sb.append(sql);
sb.append(" limit ").append(startRow).append(",").append(page.getLimit());
} else if ("hsqldb".equals(dialect)) {
sb.append("select limit ");
sb.append(startRow);
sb.append(" ");
sb.append(page.getLimit());
sb.append(" ");
sb.append(sql.substring(6));
} else if ("oracle".equals(dialect)) {
sb.append("select * from (select tmp_tb.*,ROWNUM row_id from (");
sb.append(sql);
sb.append(") tmp_tb where ROWNUM<=");
sb.append(startRow + page.getLimit());
sb.append(") where row_id>");
sb.append(startRow);
} else {
throw new IllegalArgumentException("SelectInterceptor error:does not support " + dialect);
}
return sb.toString();
}
public Object intercept(Invocation ivk) throws Throwable {
if (ivk.getTarget() instanceof RoutingStatementHandler) {
RoutingStatementHandler statementHandler = (RoutingStatementHandler) ivk.getTarget();
BaseStatementHandler delegate =
(BaseStatementHandler) Reflections.getFieldValue(statementHandler, "delegate");
MappedStatement mappedStatement =
(MappedStatement) Reflections.getFieldValue(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 {
// 生成查询总数语句,并获取总数
Connection connection = (Connection) ivk.getArgs()[0];
String sql = boundSql.getSql();
StringBuilder countSql = new StringBuilder();
countSql.append("select count(1) from (").append(sql).append(") tmp_count");
PreparedStatement countStmt = connection.prepareStatement(countSql.toString());
// BoundSql countBS = new
// BoundSql(mappedStatement.getConfiguration(),countSql.toString(),boundSql.getParameterMappings(),parameterObject);
// 使用DefaultParameterHandler来对语句进行预处理
DefaultParameterHandler defaultParameterHandler =
new DefaultParameterHandler(mappedStatement, parameterObject, boundSql);
defaultParameterHandler.setParameters(countStmt);
ResultSet rs = countStmt.executeQuery();
long count = 0;
if (rs.next()) {
count = rs.getLong(1);
}
rs.close();
countStmt.close();
// System.out.println(count);
RequestBean requestBean = null;
if (parameterObject instanceof RequestBean) { // 参数就是Page实体
requestBean = (RequestBean) parameterObject;
requestBean.setCount(count);
} else if (parameterObject instanceof Map) {
requestBean = (RequestBean) ((Map) parameterObject).get("requestBean");
requestBean.setCount(count);
} else { // 参数为某个实体，该实体拥有Page属性
Field pageField = Reflections.getAccessibleField(parameterObject, "requestBean");
if (pageField != null) {
requestBean = (RequestBean) Reflections.getFieldValue(parameterObject, "requestBean");
if (requestBean == null) requestBean = new RequestBean();
requestBean.setCount(count);
Reflections.setFieldValue(
parameterObject, "requestBean", requestBean); // 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 requestBean 属性！");
}
}
String pageSql =
dialectObj.getLimitString(sql, requestBean.getOffset(), requestBean.getPageSize());
Reflections.setFieldValue(boundSql, "sql", pageSql); // 将分页sql语句反射回BoundSql.
if (logger.isDebugEnabled()) {
logger.debug("生成分页SQL : " + boundSql.getSql());
}
}
}
}
return ivk.proceed();
}