How to get data from MYSQL database - mysql

I have a database named as "test" in which I have a table named as "first" which contains raw data, I want to get this table data. What should be the prepare statement I have to use in order to get data from table "first" ? Below is the code I am trying. Any help or guidance would be appreciable.
#Path("/database") // Specific URL
#GE
#Produces(MediaType.TEXT_PLAIN)
public String returnDB_Status() throws Exception {
PreparedStatement query = null;
String result = null;
Connection conn = null;
try {
conn = mysql_prac.dbConn().getConnection(); // this works fine ...
query = conn.prepareStatement("SELECT * from first" ); // Table named as "first" is placed inside the connected database.
ResultSet rs = query.executeQuery();
result = "Data received : " + rs;
query.close();
} catch (Exception e) {
e.printStackTrace();
} finally {
if (conn != null)
conn.close();
}
return result;
}
and the source code used get a connection
public class mysql_prac {
private static DataSource mysql_prac = null;
private static Context context = null;
public static DataSource dbConn() throws Exception {
if (mysql_prac != null) {
return mysql_prac;
}
try {
if (context == null) {
context = new InitialContext();
}
mysql_prac = (DataSource) context.lookup("JDBC_ref"); //JNDI ID (JDBC_REF)
} catch (Exception e) {
e.printStackTrace();
}
return mysql_prac;
}
}

You must loop through the ResultSet to get the fields of each row. So I made the following edit together with some comments.Please notice the comments.
try {
conn = mysql_prac.dbConn().getConnection(); // this works fine ...
query = conn.prepareStatement("SELECT * from first" ); // Table named as "first" is placed inside the connected database.
ResultSet rs = query.executeQuery();//You must loop through the results set to get the fields of each row
while(rs.next()){
String dbUserID = rs.getString("column1");//this is just an example to retrieve all data in the column called 'column1'
result = "Data received : " + dbUserID;
System.out.println(result);
}
query.close();
} catch (Exception e) {
e.printStackTrace();
} finally {
if (conn != null)
conn.close();
}

Related

Return values from database queries into a LinkedHashMap

I keep getting one value from this LinkedHashMap it's either the first [ if (resultset.next()) ] or the last [ while(resultset.next()) ], only one result is coming back but I want the full map. How do I return all rows in the table that fit my criteria? Any help would be appreciated.
/** 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;
/** A helper method was used to minimize code duplication. It works for sure */
private PreparedStatement createStatement(String query) {
try {
connection = DB_ConnectionConfiguration.getConnection();
this.query = query;
preparedStatement = connection.prepareStatement(query);
return preparedStatement;
}
catch (SQLException sqlE) {
sqlE.printStackTrace();
return null;
}
}
here are a couple suggestions in sample code below...
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;
}

how to insert settooltiptext for one vertex retrieved from MYSQLdatabase

I have developed a MySQL database with 3 different columns. Among three columns, I used 2 columns to develop a network using JUNG. Now if I place a mouse over the vertex, the corresponding information from the third column should be displayed. I have tried with the following code with the help of setVertexToolTipTransformer. But nothing is displayed as an answer.
vv.setVertexToolTipTransformer(new Transformer<String, String>() {
public String transform(String v) {
try {
String bb = "SELECT * FROM interr'";
Statement pest = connection.createStatement();
ResultSet v1 = pest.executeQuery(bb);
while(v1.next())
v= v1.getString("Pubchem_ID");
return "PUBMED:"+v.toString();
}
catch (Exception e1) {
JOptionPane.showMessageDialog(null, e1);
}
return null;
}
});
Where should i edit my code? Can anyone pls help me with this?
I got the output with the following output
vv.setVertexToolTipTransformer(new Transformer<String, String>() {
public String transform(String v) {
try {
String bb = "SELECT * FROM interr";
Statement pest = connection.createStatement();
ResultSet v1 = pest.executeQuery(bb);
while(v1.next())
if(v.toString().equals(v1.getString("Mole1")))
na[i] = v1.getString("Pubchem_ID");
System.out.println(na[i]);
v=na[i].toString();
return "PUBMED:"+v.toString();
}
catch (Exception e1) {
JOptionPane.showMessageDialog(null, e1);
}
return null;
}
});

JDBC SQL aliasing not working

I am trying to run the following query in my java web application:
SELECT platform AS "Platform" FROM edb.cases
The web-app is working fine and is able to execute all queries however whenever I use an alias (through 'AS'), the resultant data-set gives me a null value for the alias. In fact, despite using an alias for the column 'platform' in the above query, the resultant data-set has a null value for the key 'Platform' but gives me the correct value for the key 'platform' (which is the original name of the column).
Now the actual sql statement which I need to execute is a bit more complex with select statements and left joins on the same table twice using aliases, like so:
SELECT numOne.platform , numTwo.platform AS 'PlatformTwo' FROM edb.cases LEFT JOIN
edb.platform as numOne ON (numOne.rank = cases.platform) LEFT JOIN edb.platform as numTwo ON
(numTwo.rank = cases.highestPlatform) WHERE cases.index = 1000
The problem is that the resultant data-set contains the correct value for the key 'platform' (for numOne table) but the keys 'PlatformOne' and 'PlatformTwo' DO NOT EXIST. The aliases are not working!
I have tried both the statements in MySql workbench and they work fine.
Please do not hesitate to ask for more information.
EDIT:
The code that prepares the query and sends it to the database:
public static List<Map<String, Object>> executeQuery(final String query,
Map<Integer, Object> data) {
List<Map<String, Object>> result = null;
try {
Connection conn = createConnection();
PreparedStatement pstmt = null;
pstmt = conn.prepareStatement(query);
if(data != null) {
pstmt = createPreparedStatement(pstmt, data);
}
System.out.println(pstmt.toString());
//The GET_CASE_FOR_INDEX query uses the executequery function in the else block:
if((pstmt.toString().indexOf("INSERT") >= 0) || (pstmt.toString().indexOf("UPDATE") >= 0)) {
pstmt.executeUpdate();
} else {
ResultSet rs = pstmt.executeQuery();
ResultSetMetaData md = rs.getMetaData();
int columns = md.getColumnCount();
result = new ArrayList<Map<String, Object>>();
/*
* Get the next row of the ResultSet 'rs' and insert a Map of the Column/Value pair
* into the ArrayList of Maps 'result'
*/
while(rs.next()) {
Map<String, Object> row = new HashMap<String, Object>(columns);
for(int i=1; i <= columns; i++) {
try {
row.put(md.getColumnName(i), rs.getObject(i));
} catch(Exception e) {
System.out.println(md.getColumnName(i));
System.out.println(row);
e.printStackTrace();
}
}
result.add(row);
}
}
destroyConnection(conn);
pstmt.close();
} catch(SQLException e) {
//TODO
e.printStackTrace();
}
return result;
}
The function creating the prepared statement:
//creates a prepared statement by checking the type of the value that needs to be set.
private static PreparedStatement createPreparedStatement(
PreparedStatement pstmt, Map<Integer, Object> data) {
try {
for(Integer key : data.keySet()) {
Object value = data.get(key);
System.out.println(key);
if(data.get(key).equals(Types.NULL)) {
pstmt.setNull(key, Types.INTEGER);
} else if(value.getClass().equals(Integer.class)) {
pstmt.setInt(key, (Integer) value);
} else if(value.getClass().equals(String.class)) {
pstmt.setString(key, (String) value);
} else if(value.getClass().equals(Date.class)) {
pstmt.setDate(key, (Date) value);
} else if(value.getClass().equals(Timestamp.class)) {
pstmt.setTimestamp(key, (Timestamp) value);
}
}
}catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return pstmt;
}
And the code snippet which uses the executeQuery function to execute the query and sends it to the web template:
Map<Integer, Object> data_details = new HashMap<Integer, Object>();
data_details.put(1, parameter_ID);
List<Map<String, Object>> details = DBUtility.executeQuery(DBQuery.GET_CASE_FOR_INDEX, data_details);
webContext.setVariable("details", details);//This is where the template variable is being set
System.out.println(details);
The GET_CASE_FOR_INDEX query is :
SELECT numOne.platform , numTwo.platform AS 'PlatformTwo' FROM edb.cases LEFT JOIN
edb.platform as numOne ON (numOne.rank = cases.platform) LEFT JOIN edb.platform as numTwo ON
(numTwo.rank = cases.highestPlatform) WHERE cases.index = ?
When I print the details hash map (which is the result data-set) the key PlatformTwo is entirely absent!
You are using the .getColumnName method of ResultSetMetaData, which returns the name of the underlying column (if available). .getColumnLabel will return the column alias as defined by SELECT ... AS ....
To illustrate, the following Java code
PreparedStatement ps = conn.prepareStatement(
"SELECT platform AS Platypus FROM cases");
ResultSet rs = ps.executeQuery();
ResultSetMetaData rsmd = rs.getMetaData();
System.out.println(String.format(
".getColumnName returns \"%s\"",
rsmd.getColumnName(1)));
System.out.println(String.format(
".getColumnLabel returns \"%s\"",
rsmd.getColumnLabel(1)));
returns
.getColumnName returns "platform"
.getColumnLabel returns "Platypus"

Retrieving data from mysql in Java

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
try
{
Class.forName("java.sql.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/mysql", "root", "parin");
Statement stmt=con.createStatement();
String query="Select * from Liblogin;";
ResultSet rs=stmt.executeQuery(query);
String username=rs.getString("username");
String password=rs.getString("password");
rs.close();
stmt.close();
con.close();
String enteredUsername=t1.getText().toString();
String enteredPassword = new String(t2.getText());
if(enteredUsername.contentEquals(username)&&enteredPassword.contentEquals(password))
{
Homepage a=new Homepage();
a.setVisible(true);
this.dispose();
}
else
{
JOptionPane.showMessageDialog(this,"Incorrect name and password.");
}
}
catch(Exception e)
{
JOptionPane.showMessageDialog(this, e);
}
}
I am trying to retrieve my password and username from mysql database.But unable to do so because of some exception(Sql exception:Before start of result set.).
You need to call rs.first(); or rs.next(); before trying to read the values from a ResultSet row.
http://docs.oracle.com/javase/6/docs/api/java/sql/ResultSet.html#first%28%29
Calling rs.next(); is especially handy in a while-loop to process all the rows in the ResultSet.
// Get a result set from SQL query
while (rs.next()) {
// Process this row
}

Store the results of ResultSet in a list

My goal is to centralize all the interactions with my MySql database in a single class (e.g. SqlUtils). I basically want to maintain access to ResultSet or a similar class even after the connection is closed. The following way doesn't work as after my business method receives the ResultSet, an exception is thrown because the underlying connection is already closed. I want to emphasize that opening and closing a connection to the database has to take place inside getResultSet().
public ResultSet getResultSet(String sql) {
try (Connection conn = getConnection();){
return conn.createStatement().executeQuery(sql);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
What I'm now thinking to do is something like this:
public List<ResultHolder> getResultSet(String sql) {
List<ResultHolder> list = new LinkedList<>();
try (Connection conn = getConnection();
ResultSet res = conn.createStatement().executeQuery(sql);) {
while(res.next()) {
list.add(res.convertToResultHolder());
}
} catch (Exception e) {
e.printStackTrace();
}
return list;
}
Is there any class that does what I need, which I expressed as ResultHolder.
If you want to have access to all the resultset data even after connection is closed then I would suggest following:
public List<Map<String, Object>> getResultSet(String sql) {
// this list will hold all the data returned from resultset
List<Map<String, Object>> rows = new ArrayList<Map<String, Object>>();
try (Connection conn = getConnection();
ResultSet rs = conn.createStatement().executeQuery(sql);) {
while(rs.next()) {
// this map corresponds to each row of the resultset
// key: column-name, value: column-value
Map<String, Object> row = new LinkedHashMap<String, Object>();
// populate each row using resultset's Meta data
ResultSetMetaData meta = rs.getMetaData();
for (int i=1; i<=meta.getColumnCount(); i++)
row.put(meta.getColumnName(i), rs.getObject(i));
rows.add(row);
}
} catch (Exception e) {
e.printStackTrace();
}
return rows;
}