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1
28
29 import java.sql.Connection  ;
30 import java.sql.PreparedStatement ;
31 import java.sql.ResultSet ;
32 import java.sql.Statement ;
33
34 import javax.naming.InitialContext ;
35 import javax.sql.DataSource ;
36 import javax.transaction.UserTransaction ;
37
38
41 public class DistributedDataSourceExample {
42
43 private static final String SQL_REQUEST = "select id, foo from testdata";
44
45 private static final String SQL_QUERY =
46 "update testdata set foo = ? where id=1";
47
48 private static Connection conn;
49
50 private static void updateTable(int newValue) {
51 try {
52 Statement stmt = conn.createStatement();
53 PreparedStatement pstmt = conn.prepareStatement(SQL_QUERY);
54 pstmt.setInt(1, newValue);
55 pstmt.executeUpdate();
56 } catch (Exception e) {
57 e.printStackTrace();
58 }
59 }
60
61 private static void printTable() {
62 try {
63 Statement stmt = conn.createStatement();
64 ResultSet rset = stmt.executeQuery(SQL_REQUEST);
65 int numcols = rset.getMetaData().getColumnCount();
66 for (int i = 1; i <= numcols; i++) {
67 System.out.print("\t" + rset.getMetaData().getColumnName(i));
68 }
69 System.out.println();
70 while (rset.next()) {
71 for (int i = 1; i <= numcols; i++) {
72 System.out.print("\t" + rset.getString(i));
73 }
74 System.out.println("");
75 }
76 } catch (Exception e) {
77 e.printStackTrace();
78 }
79 }
80
81 public static void main(String [] args) {
82
83 if (args.length != 2|| (!args[0].equals("commit") && !args[0].equals("rollback"))) {
84 System.err.println("usage: java DistributedDataSourceExample [completion] [number]\n");
85 System.exit(1);
86 }
87
88 String completion = args[0];
89 int value = 0;
90 try {
91 value = Integer.parseInt(args[1]);
92 } catch (NumberFormatException e) {
93 System.out.println("[number] has to be an integer\n");
94 System.exit(1);
95 }
96
97 UserTransaction utx = null;
98 try {
99 System.out.println("create initial context");
100 InitialContext ictx = new InitialContext ();
101 System.out.println("lookup UserTransaction at : UserTransaction");
102 utx = (UserTransaction ) ictx.lookup("UserTransaction");
103 System.out.println("lookup DataSource at: DataSource");
104 DataSource ds = (DataSource ) ictx.lookup("DataSource");
105 System.out.println("get a connection");
106 conn = ds.getConnection("mojo", "jojo");
107 } catch (Exception e) {
108 System.out.println(
109 "Exception of type :"
110 + e.getClass().getName()
111 + " has been thrown");
112 System.out.println("Exception message :" + e.getMessage());
113 e.printStackTrace();
114 System.exit(1);
115 }
116
117 System.out.println("before transaction, table is:");
118 printTable();
119
120 try {
121 System.out.println("begin a transaction");
122 utx.begin();
123
124 System.out.println("update the table");
125 updateTable(value);
126
127 if (completion.equals("commit")) {
128 System.out.println("*commit* the transaction");
129 utx.commit();
130 } else {
131 System.out.println("*rollback* the transaction");
132 utx.rollback();
133 }
134 } catch (Exception e) {
135 System.out.println(
136 "Exception of type :"
137 + e.getClass().getName()
138 + " has been thrown");
139 System.out.println("Exception message :" + e.getMessage());
140 e.printStackTrace();
141 System.exit(1);
142 }
143
144 System.out.println("after transaction, table is:");
145 printTable();
146 System.out.println("Recovery Example is ok.\n");
147 System.exit(0);
148 }
149 }
150
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Java API By Example, From Geeks To Geeks.