Mysql 将数据库查询中的值返回到LinkedHashMap中
我一直从这个LinkedHashMap中得到一个值,要么是第一个[if(resultset.next())],要么是最后一个[while(resultset.next())],只返回一个结果,但我想要完整的映射。如何返回表中符合条件的所有行?任何帮助都将不胜感激Mysql 将数据库查询中的值返回到LinkedHashMap中,mysql,jdbc,linkedhashmap,rowcount,Mysql,Jdbc,Linkedhashmap,Rowcount,我一直从这个LinkedHashMap中得到一个值,要么是第一个[if(resultset.next())],要么是最后一个[while(resultset.next())],只返回一个结果,但我想要完整的映射。如何返回表中符合条件的所有行?任何帮助都将不胜感激 /** A method to list all previous statuses for a certain user given the userID */ public StringBuilder showStatusHist
/** A method to list all previous statuses for a certain user given the userID */
public StringBuilder showStatusHistory(int userID) {
try {
Date date;
String status;
preparedStatement = createStatement("select statusDate,statusText from statusTable where userID = ?");
preparedStatement.setInt(1,userID);
resultSet = preparedStatement.executeQuery();
StringBuilder allStatus = new StringBuilder("");
statusesList = new LinkedHashMap<>();
while (resultSet.next()){
date = resultSet.getDate(1);
status = resultSet.getString(2);
statusesList.put(date,status);
}
Set<Date> statusTime = statusesList.keySet();
for(Date k:statusTime){
allStatus.append(k+" "+statusesList.get(k));
}
return allStatus;
}
catch (SQLException sqlE){
sqlE.printStackTrace();
}
return null;
下面的示例代码中有一些建议
public StringBuilder showStatusHistory(int userID) {
// define at top and return "" if no results
StringBuilder allStatus = new StringBuilder("");
try {
Date date;
String status;
// define local in the method
PreparedStatement preparedStatement = createStatement("select statusDate,statusText from statusTable where userID = ?");
preparedStatement.setInt(1, userID);
// define local in the method
ResultSet resultSet = preparedStatement.executeQuery();
// append to the all Status here and skip the other loop
// if you need a distinct list (like you had fro the Set) you could use a DISTINCT on the SQL statement.
while (resultSet.next()) {
date = resultSet.getDate(1);
status = resultSet.getString(2);
// append to the allStatus here
allStatus.append(date).append(" ").append(status); // add a newline to the end? append(System.lineSeparator())
}
} catch (SQLException sqlE) {
sqlE.printStackTrace();
// do you want to throw this if something bad happened?
} finally {
// close up your jdbc resources
}
// will contain "" if no records or concatenated statuses from the resultset
return allStatus;
}
public StringBuilder showStatusHistory(int userID) {
// define at top and return "" if no results
StringBuilder allStatus = new StringBuilder("");
try {
Date date;
String status;
// define local in the method
PreparedStatement preparedStatement = createStatement("select statusDate,statusText from statusTable where userID = ?");
preparedStatement.setInt(1, userID);
// define local in the method
ResultSet resultSet = preparedStatement.executeQuery();
// append to the all Status here and skip the other loop
// if you need a distinct list (like you had fro the Set) you could use a DISTINCT on the SQL statement.
while (resultSet.next()) {
date = resultSet.getDate(1);
status = resultSet.getString(2);
// append to the allStatus here
allStatus.append(date).append(" ").append(status); // add a newline to the end? append(System.lineSeparator())
}
} catch (SQLException sqlE) {
sqlE.printStackTrace();
// do you want to throw this if something bad happened?
} finally {
// close up your jdbc resources
}
// will contain "" if no records or concatenated statuses from the resultset
return allStatus;
}