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Groups > comp.lang.java.programmer > #37121
| From | Arne Vajhøj <arne@vajhoej.dk> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: Is this the way to work with try with resources |
| Date | 2017-08-09 20:53 -0400 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <omgapf$dlf$1@gioia.aioe.org> (permalink) |
| References | <87poc6wb9n.fsf@munus.decebal.nl> <omdob4$cif$1@gioia.aioe.org> <omdovg$d4o$1@gioia.aioe.org> <87k22dux5g.fsf@munus.decebal.nl> |
On 8/9/2017 1:29 AM, Cecil Westerhof wrote:
> I now have:
> try (ResultSet rsTotal = conn.createStatement().executeQuery(COUNT_TOTAL_PROV);
> ResultSet rsUnused = conn.createStatement().executeQuery(COUNT_UNUSED_PROV);
> ResultSet rsUsed = conn.createStatement().executeQuery(COUNT_USED_PROV)) {
>
> That could go wrong?
Lots.
See previous posts.
> If so: is there a way to verify if it goes OK, or
> wrong?
Interesting question.
There are probably many approaches.
But here is one.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DBCode {
public static void main(String[] args) throws SQLException {
Connection con =
DriverManager.getConnection("jdbc:mysql://localhost/Test", "root", "");
con = Reveal.wrap(con); // <----
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("SELECT f1,f2 fROM t1");
while(rs.next()) {
System.out.printf("%d %s\n", rs.getInt(1), rs.getString(2));
}
//rs.close();
//stmt.close();
PreparedStatement pstmt = con.prepareStatement("SELECT f1,f2
fROM t1 WHERE f1 > ?");
pstmt.setInt(1, 2);
ResultSet prs = pstmt.executeQuery();
while(prs.next()) {
System.out.printf("%d %s\n", prs.getInt(1), prs.getString(2));
}
//prs.close();
//pstmt.close();
//con.close();
Reveal.dumpOpen(System.out); // <----
}
}
Output:
Unclosed: Connection#1
Unclosed: ResultSet#2 from PreparedStatement#1 (SELECT f1,f2 fROM t1
WHERE f1 > ?) from Connection#1
Unclosed: Statement#1 from Connection#1
Unclosed: PreparedStatement#1 (SELECT f1,f2 fROM t1 WHERE f1 > ?) from
Connection#1
Unclosed: ResultSet#1 (SELECT f1,f2 fROM t1) from Statement#1 from
Connection#1
The "magic" sauce:
import java.io.PrintStream;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.HashSet;
import java.util.Set;
public class Reveal {
public static interface TrackableResource {
public String getId() throws SQLException;
}
private static Set<TrackableResource> reslst = new
HashSet<TrackableResource>();
public static class ResultSetWrapper implements InvocationHandler,
TrackableResource {
private static int count = 0;
private int num;
private ResultSet rs;
private String parent;
private String sql;
public ResultSetWrapper(ResultSet rs, String parent) {
this.rs = rs;
this.parent = parent;
this.sql = null;
synchronized(reslst) {
count++;
num = count;
reslst.add(this);
}
}
public ResultSetWrapper(ResultSet rs, String parent, String sql) {
this.rs = rs;
this.parent = parent;
this.sql = sql;
synchronized(reslst) {
count++;
num = count;
reslst.add(this);
}
}
public Object invoke(Object proxy, Method method, Object[]
args) throws Throwable {
if(method.getName().equals("close")) {
reslst.remove(this);
return method.invoke(rs, args);
} else {
return method.invoke(rs, args);
}
}
public String getId() throws SQLException {
if(sql == null) {
return "ResultSet#" + num + " from " + parent;
} else {
return "ResultSet#" + num + " (" + sql + ") from " +
parent;
}
}
}
public static class PreparedStatementWrapper implements
InvocationHandler, TrackableResource {
private static int count = 0;
private int num;
private Statement stmt;
private String parent;
private String sql;
public PreparedStatementWrapper(Statement stmt, String parent,
String sql) {
this.stmt = stmt;
this.parent = parent;
this.sql = sql;
synchronized(reslst) {
count++;
num = count;
reslst.add(this);
}
}
public Object invoke(Object proxy, Method method, Object[]
args) throws Throwable {
if(method.getName().equals("close")) {
reslst.remove(this);
return method.invoke(stmt, args);
} else if(method.getName().equals("executeQuery")) {
return
(ResultSet)Proxy.newProxyInstance(getClass().getClassLoader(), new
Class<?>[] { ResultSet.class },
new
ResultSetWrapper((ResultSet)method.invoke(stmt, args), getId()));
} else {
return method.invoke(stmt, args);
}
}
public String getId() throws SQLException {
return "PreparedStatement#" + num + " (" + sql + ") from "
+ parent;
}
}
public static class StatementWrapper implements InvocationHandler,
TrackableResource {
private static int count = 0;
private int num;
private Statement stmt;
private String parent;
public StatementWrapper(Statement stmt, String parent) {
this.stmt = stmt;
this.parent = parent;
synchronized(reslst) {
count++;
num = count;
reslst.add(this);
}
}
public Object invoke(Object proxy, Method method, Object[]
args) throws Throwable {
if(method.getName().equals("close")) {
reslst.remove(this);
return method.invoke(stmt, args);
} else if(method.getName().equals("executeQuery")) {
return
(ResultSet)Proxy.newProxyInstance(getClass().getClassLoader(), new
Class<?>[] { ResultSet.class },
new
ResultSetWrapper((ResultSet)method.invoke(stmt, args), getId(),
(String)args[0]));
} else {
return method.invoke(stmt, args);
}
}
public String getId() throws SQLException {
return "Statement#" + num + " from " + parent;
}
}
public static class ConnectionWrapper implements InvocationHandler,
TrackableResource {
private static int count = 0;
private int num;
private Connection con;
public ConnectionWrapper(Connection con) {
this.con = con;
synchronized(reslst) {
count++;
num = count;
reslst.add(this);
}
}
public Object invoke(Object proxy, Method method, Object[]
args) throws Throwable {
if(method.getName().equals("close")) {
reslst.remove(this);
return method.invoke(con, args);
} else if(method.getName().equals("createStatement")) {
return
(Statement)Proxy.newProxyInstance(con.getClass().getClassLoader(), new
Class<?>[] { Statement.class },
new
StatementWrapper((Statement)method.invoke(con, args), getId()));
} else if(method.getName().equals("prepareStatement")) {
return
(PreparedStatement)Proxy.newProxyInstance(con.getClass().getClassLoader(),
new Class<?>[] { PreparedStatement.class },
new
PreparedStatementWrapper((PreparedStatement)method.invoke(con, args),
getId(), (String)args[0]));
} else {
return method.invoke(con, args);
}
}
public String getId() throws SQLException {
return "Connection#" + num;
}
}
public static Connection wrap(Connection con) {
return
(Connection)Proxy.newProxyInstance(con.getClass().getClassLoader(), new
Class<?>[] { Connection.class },
new
ConnectionWrapper(con));
}
public static void dumpOpen(PrintStream ps) throws SQLException {
for(TrackableResource obj : reslst.toArray(new
TrackableResource[0])) {
System.out.println("Unclosed: " + obj.getId());
}
}
}
Arne
Back to comp.lang.java.programmer | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-08 13:26 +0200
Re: Is this the way to work with try with resources Martin Gregorie <martin@address-in-sig.invalid> - 2017-08-08 12:51 +0000
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 07:10 +0200
Re: Is this the way to work with try with resources Patrick Roemer <sangamon@netcologne.de> - 2017-08-08 18:29 +0200
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 07:20 +0200
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 07:16 +0200
Re: Is this the way to work with try with resources Patrick Roemer <sangamon@netcologne.de> - 2017-08-08 19:30 +0200
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 06:49 +0200
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 07:01 +0200
Re: Is this the way to work with try with resources Patrick Roemer <sangamon@netcologne.de> - 2017-08-09 15:39 +0200
Re: Is this the way to work with try with resources Arne Vajhøj <arne@vajhoej.dk> - 2017-08-08 21:25 -0400
Re: Is this the way to work with try with resources Arne Vajhøj <arne@vajhoej.dk> - 2017-08-08 21:36 -0400
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 07:29 +0200
Re: Is this the way to work with try with resources Arne Vajhøj <arne@vajhoej.dk> - 2017-08-09 20:53 -0400
Re: Is this the way to work with try with resources Arne Vajhøj <arne@vajhoej.dk> - 2017-08-09 23:03 -0400
Re: Is this the way to work with try with resources Arne Vajhøj <arne@vajhoej.dk> - 2017-08-08 21:48 -0400
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 07:24 +0200
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 06:26 +0200
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 08:30 +0200
Re: Is this the way to work with try with resources Andreas Leitgeb <avl@logic.at> - 2017-08-09 09:40 +0000
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 12:56 +0200
Re: Is this the way to work with try with resources Andreas Leitgeb <avl@logic.at> - 2017-08-09 16:51 +0000
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 19:37 +0200
Re: Is this the way to work with try with resources Andreas Leitgeb <avl@logic.at> - 2017-08-09 19:51 +0000
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 22:20 +0200
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 23:17 +0200
Re: Is this the way to work with try with resources Patrick Roemer <sangamon@netcologne.de> - 2017-08-09 22:08 +0200
Re: Is this the way to work with try with resources Arne Vajhøj <arne@vajhoej.dk> - 2017-08-09 18:07 -0400
Re: Is this the way to work with try with resources Arne Vajhøj <arne@vajhoej.dk> - 2017-08-09 18:05 -0400
Re: Is this the way to work with try with resources Cecil Westerhof <Cecil@decebal.nl> - 2017-08-09 06:39 +0200
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