java: display the elements from a database

Question

I wrote some java code to display database, when I run the code it gives me just the last element of database , but I wanna display all elements of table

the code :

public String RecupererPuissance() {
    try {
        Connection con =  myDbvoiture.getConnection();
        String queryPattern ="select Power from bd_voiture";
        PreparedStatement pstmt =  con.prepareStatement(queryPattern);
        ResultSet rs = pstmt.executeQuery();
        while (rs.next()) {
            puissance=rs.getString("Power");
            System.out.println(puissance);
        }
    } catch (SQLException ex) {
        System.err.println(ex.getMessage());
    }
    return puissance;
}

What should I do? Can anyone please help me to display all values? Thank you for helping me.

Your code looks correct. How many elements are inside the table bd_voiture? Also, how many elements inside the Resultset rs? Also, try to pass an order by clause to that select, so you get predictable results (select get unordered results by default) — Diego Freniche
– Diego Freniche, Commented May 26, 2016 at 9:47
@DiegoFreniche thank you for your help, I have 40 elements in my table , but one element inside the Resultset. — Sunny Hill
– Sunny Hill, Commented May 26, 2016 at 10:20
Do you get all 40 elements printed by that println? Also, look JHead answer — Diego Freniche
– Diego Freniche, Commented May 26, 2016 at 10:25

JHead · Accepted Answer · 2016-05-26 09:55:53Z

1

I think the problem is with your code that the value of puissance is overwritten every time you get the next element. Only the last value is returned. You should put the results into a list and return the whole list:

public List<String> RecupererPuissance() {
    List<String> puissances = new ArrayList<String>();
    try {
        Connection con =  myDbvoiture.getConnection();
        String queryPattern ="select Power from bd_voiture";
        PreparedStatement pstmt =  con.prepareStatement(queryPattern);
        ResultSet rs = pstmt.executeQuery();
        while (rs.next()) {
            puissance = rs.getString("Power");
            puissances.add(puissance);
            System.out.println(puissance);
        }
    } catch (SQLException ex) {
        System.err.println(ex.getMessage());
    }
    return puissances;
}

edited May 26, 2016 at 9:55

answered May 26, 2016 at 9:52

JHead

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5 Comments

Draken Over a year ago

You need to correct the following lines: puissances.add(rs.getString("Power")); System.out.println(puissance); to be puissance = rs.getString("Power"); puissances.add(puissance); System.out.println(puissance); At the moment, your puissance isn't being set, which could cause issues at the print line statement

Sunny Hill Over a year ago

Thank you for helping me with this matter, I did that but nothing has changed , i don't understand why?

Sunny Hill Over a year ago

@Draken when i change my code and call my web service i used this code ` mws.MyWebService_Service service = new mws.MyWebService_Service(); mws.MyWebService port = service.getMyWebServicePort(); String puis= port.recupererPuissance(); System.out.println(puis); ` do you think the problem is in this a part

Draken Over a year ago

It is, it should be: List<String> puisList= port.recupererPuissance(); instead of String puis= port.recupererPuissance(); Then you could iterate it using a for loop, as an example. So if you want to print it, it would be: for(String puis : puisList) System.out.println(puis);

Sunny Hill Over a year ago

@Draken Great, My code is working , thank you very much for your reply.

vibhor vaish · Accepted Answer · 2016-05-26 17:16:01Z

0

public String RecupererPuissance() {
    try {
        Connection con =  myDbvoiture.getConnection();
        String queryPattern ="select Power from bd_voiture";
        PreparedStatement pstmt =  con.prepareStatement(queryPattern);
        ResultSet rs = pstmt.executeQuery();
        rs.first();
        int count=0;
        while (rs.next()) {
        System.out.println("count = "+count);
        count+=1;
            puissance=rs.getString("Power");
            System.out.println(puissance);
        }
    } catch (SQLException ex) {
        System.err.println(ex.getMessage());
    }
    return puissance;
}

If you see count printed only 1 time :

it would mean that you have only 1 row in column Power and you maybe referring to the wrong column in your code

edited May 26, 2016 at 17:16

answered May 26, 2016 at 10:07

vibhor vaish

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1 Comment

Sunny Hill Over a year ago

thank you for your help, I did that but nothing has changed

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