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368 lines
12 KiB
Java
368 lines
12 KiB
Java
package example;
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import java.io.*;
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import java.sql.*;
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import java.text.*;
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// rare in user code, but we use the LargeObject API in this test
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import org.postgresql.largeobject.*;
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/**
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* This example tests the thread safety of the driver.
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*
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* It does this by performing several queries, in different threads. Each
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* thread has it's own Statement object, which is (in my understanding of the
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* jdbc specification) the minimum requirement.
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*
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*/
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public class threadsafe
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{
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Connection db; // The connection to the database
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Statement st; // Our statement to run queries with
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public threadsafe(String args[]) throws ClassNotFoundException, FileNotFoundException, IOException, SQLException
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{
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String url = args[0];
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String usr = args[1];
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String pwd = args[2];
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// Load the driver
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Class.forName("org.postgresql.Driver");
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// Connect to database
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System.out.println("Connecting to Database URL = " + url);
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db = DriverManager.getConnection(url, usr, pwd);
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System.out.println("Connected...Now creating a statement");
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st = db.createStatement();
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// Clean up the database (in case we failed earlier) then initialise
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cleanup();
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// Because we use LargeObjects, we must use Transactions
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db.setAutoCommit(false);
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// Now run tests using JDBC methods, then LargeObjects
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doexample();
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// Clean up the database
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cleanup();
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// Finally close the database
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System.out.println("Now closing the connection");
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st.close();
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db.close();
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}
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/**
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* This drops the table (if it existed). No errors are reported.
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*/
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public void cleanup()
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{
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try {
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st.executeUpdate("drop table basic1");
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} catch(Exception ex) {
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// We ignore any errors here
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}
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try {
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st.executeUpdate("drop table basic2");
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} catch(Exception ex) {
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// We ignore any errors here
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}
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}
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/**
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* This performs the example
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*/
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public void doexample() throws SQLException
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{
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System.out.println("\nThis test runs three Threads. Two simply insert data into a table, then\nthey perform a query. While they are running, a third thread is running,\nand it load data into, then reads from a Large Object.\n\nIf alls well, this should run without any errors. If so, we are Thread Safe.\nWhy test JDBC & LargeObject's? Because both will run over the network\nconnection, and if locking on the stream isn't done correctly, the backend\nwill get pretty confused!\n");
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thread3 thread3=null;
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try {
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// create the two threads
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Thread thread0 = Thread.currentThread();
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Thread thread1 = new thread1(db);
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Thread thread2 = new thread2(db);
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thread3 = new thread3(db);
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// now run, and wait for them
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thread1.start();
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thread2.start();
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thread3.start();
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// ok, I know this is bad, but it does the trick here as our main thread
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// will yield as long as either of the children are still running
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System.out.println("Waiting for threads to run");
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while(thread1.isAlive() || thread2.isAlive() || thread3.isAlive())
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thread0.yield();
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} finally {
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// clean up after thread3 (the finally ensures this is run even
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// if an exception is thrown inside the try { } construct)
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if(thread3 != null)
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thread3.cleanup();
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}
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System.out.println("No Exceptions have been thrown. This is a good omen, as it means that we are\npretty much thread safe as we can get.");
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}
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// This is the first thread. It's the same as the basic test
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class thread1 extends Thread
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{
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Connection c;
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Statement st;
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public thread1(Connection c) throws SQLException {
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this.c = c;
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st = c.createStatement();
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}
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public void run() {
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try {
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System.out.println("Thread 1 running...");
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// First we need a table to store data in
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st.executeUpdate("create table basic1 (a int2, b int2)");
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// Now insert some data, using the Statement
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st.executeUpdate("insert into basic1 values (1,1)");
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st.executeUpdate("insert into basic1 values (2,1)");
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st.executeUpdate("insert into basic1 values (3,1)");
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// For large inserts, a PreparedStatement is more efficient, because it
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// supports the idea of precompiling the SQL statement, and to store
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// directly, a Java object into any column. PostgreSQL doesnt support
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// precompiling, but does support setting a column to the value of a
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// Java object (like Date, String, etc).
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//
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// Also, this is the only way of writing dates in a datestyle independent
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// manner. (DateStyles are PostgreSQL's way of handling different methods
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// of representing dates in the Date data type.)
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PreparedStatement ps = db.prepareStatement("insert into basic1 values (?,?)");
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for(int i=2;i<2000;i++) {
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ps.setInt(1,4); // "column a" = 5
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ps.setInt(2,i); // "column b" = i
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ps.executeUpdate(); // executeUpdate because insert returns no data
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// c.commit();
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if((i%50)==0)
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DriverManager.println("Thread 1 done "+i+" inserts");
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}
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ps.close(); // Always close when we are done with it
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// Finally perform a query on the table
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DriverManager.println("Thread 1 performing a query");
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ResultSet rs = st.executeQuery("select a, b from basic1");
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int cnt=0;
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if(rs!=null) {
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// Now we run through the result set, printing out the result.
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// Note, we must call .next() before attempting to read any results
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while(rs.next()) {
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int a = rs.getInt("a"); // This shows how to get the value by name
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int b = rs.getInt(2); // This shows how to get the value by column
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//System.out.println(" a="+a+" b="+b);
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cnt++;
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}
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rs.close(); // again, you must close the result when done
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}
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DriverManager.println("Thread 1 read "+cnt+" rows");
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// The last thing to do is to drop the table. This is done in the
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// cleanup() method.
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System.out.println("Thread 1 finished");
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} catch(SQLException se) {
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System.err.println("Thread 1: "+se.toString());
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se.printStackTrace();
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System.exit(1);
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}
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}
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}
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// This is the second thread. It's the similar to the basic test, and thread1
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// except it works on another table.
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class thread2 extends Thread
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{
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Connection c;
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Statement st;
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public thread2(Connection c) throws SQLException {
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this.c = c;
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st = c.createStatement();
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}
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public void run() {
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try {
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System.out.println("Thread 2 running...");
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// First we need a table to store data in
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st.executeUpdate("create table basic2 (a int2, b int2)");
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// For large inserts, a PreparedStatement is more efficient, because it
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// supports the idea of precompiling the SQL statement, and to store
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// directly, a Java object into any column. PostgreSQL doesnt support
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// precompiling, but does support setting a column to the value of a
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// Java object (like Date, String, etc).
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//
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// Also, this is the only way of writing dates in a datestyle independent
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// manner. (DateStyles are PostgreSQL's way of handling different methods
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// of representing dates in the Date data type.)
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PreparedStatement ps = db.prepareStatement("insert into basic2 values (?,?)");
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for(int i=2;i<2000;i++) {
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ps.setInt(1,4); // "column a" = 5
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ps.setInt(2,i); // "column b" = i
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ps.executeUpdate(); // executeUpdate because insert returns no data
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// c.commit();
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if((i%50)==0)
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DriverManager.println("Thread 2 done "+i+" inserts");
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}
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ps.close(); // Always close when we are done with it
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// Finally perform a query on the table
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DriverManager.println("Thread 2 performing a query");
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ResultSet rs = st.executeQuery("select * from basic2 where b>1");
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int cnt=0;
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if(rs!=null) {
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// First find out the column numbers.
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//
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// It's best to do this here, as calling the methods with the column
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// numbers actually performs this call each time they are called. This
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// really speeds things up on large queries.
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//
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int col_a = rs.findColumn("a");
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int col_b = rs.findColumn("b");
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// Now we run through the result set, printing out the result.
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// Again, we must call .next() before attempting to read any results
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while(rs.next()) {
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int a = rs.getInt(col_a); // This shows how to get the value by name
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int b = rs.getInt(col_b); // This shows how to get the value by column
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//System.out.println(" a="+a+" b="+b);
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cnt++;
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}
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rs.close(); // again, you must close the result when done
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}
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DriverManager.println("Thread 2 read "+cnt+" rows");
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// The last thing to do is to drop the table. This is done in the
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// cleanup() method.
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System.out.println("Thread 2 finished");
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} catch(SQLException se) {
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System.err.println("Thread 2: "+se.toString());
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se.printStackTrace();
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System.exit(1);
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}
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}
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}
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// This is the third thread. It loads, then reads from a LargeObject, using
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// our LargeObject api.
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//
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// The purpose of this is to test that FastPath will work in between normal
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// JDBC queries.
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class thread3 extends Thread
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{
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Connection c;
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Statement st;
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LargeObjectManager lom;
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LargeObject lo;
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int oid;
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public thread3(Connection c) throws SQLException {
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this.c = c;
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//st = c.createStatement();
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// create a blob
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lom = ((org.postgresql.Connection)c).getLargeObjectAPI();
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oid = lom.create();
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System.out.println("Thread 3 has created a blob of oid "+oid);
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}
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public void run() {
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try {
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System.out.println("Thread 3 running...");
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DriverManager.println("Thread 3: Loading data into blob "+oid);
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lo = lom.open(oid);
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FileInputStream fis = new FileInputStream("example/threadsafe.java");
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// keep the buffer size small, to allow the other thread a chance
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byte buf[] = new byte[128];
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int rc,bc=1,bs=0;
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while((rc=fis.read(buf))>0) {
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DriverManager.println("Thread 3 read block "+bc+" "+bs+" bytes");
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lo.write(buf,0,rc);
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bc++;
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bs+=rc;
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}
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lo.close();
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fis.close();
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DriverManager.println("Thread 3: Reading blob "+oid);
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lo=lom.open(oid);
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bc=0;
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while(buf.length>0) {
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buf=lo.read(buf.length);
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if(buf.length>0) {
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String s = new String(buf);
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bc++;
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DriverManager.println("Thread 3 block "+bc);
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DriverManager.println("Block "+bc+" got "+s);
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}
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}
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lo.close();
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System.out.println("Thread 3 finished");
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} catch(Exception se) {
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System.err.println("Thread 3: "+se.toString());
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se.printStackTrace();
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System.exit(1);
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}
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}
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public void cleanup() throws SQLException {
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if(lom!=null && oid!=0) {
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System.out.println("Thread 3: Removing blob oid="+oid);
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lom.delete(oid);
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}
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}
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}
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/**
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* Display some instructions on how to run the example
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*/
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public static void instructions()
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{
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System.out.println("\nThis tests the thread safety of the driver.\n\nThis is done in two parts, the first with standard JDBC calls, and the\nsecond mixing FastPath and LargeObject calls with queries.\n");
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System.out.println("Useage:\n java example.threadsafe jdbc:postgresql:database user password [debug]\n\nThe debug field can be anything. It's presence will enable DriverManager's\ndebug trace. Unless you want to see screens of items, don't put anything in\nhere.");
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System.exit(1);
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}
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/**
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* This little lot starts the test
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*/
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public static void main(String args[])
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{
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System.out.println("PostgreSQL Thread Safety test v6.4 rev 1\n");
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if(args.length<3)
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instructions();
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// This line outputs debug information to stderr. To enable this, simply
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// add an extra parameter to the command line
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if(args.length>3)
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DriverManager.setLogStream(System.err);
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// Now run the tests
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try {
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threadsafe test = new threadsafe(args);
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} catch(Exception ex) {
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System.err.println("Exception caught.\n"+ex);
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ex.printStackTrace();
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}
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}
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}
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