| 1 | <head><title>FAQ for JavaGDBM</title>
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| 2 | </head>
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| 3 |
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| 4 | <h1>FAQ for JavaGDBM</h1>
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| 5 | <p><pre>$Id: FAQ.html 10737 2005-10-19 03:06:40Z kjdon $</pre>
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| 6 | <p><a href="http://www.pharos.com.au/gdbm/"><b>Home page</b></a> |
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| 7 | <a href="mailto:[email protected]"><b>[email protected]</b></a>
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| 8 |
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| 9 | <p><b>This is not an official publication of Pharos. There is no
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| 10 | warranty of any kind on this software or document.</b>
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| 11 |
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| 12 | <h3>Is this a JDBC driver?</h3>
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| 13 |
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| 14 | <p>(Alain Magloire)
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| 15 |
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| 16 | <p>No. JDBC seems mainly intended for interfaces to relational
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| 17 | databases, and GDBM is not a relational database.
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| 18 |
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| 19 | <p>However, JDBC does permit use of a subset to interface to
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| 20 | non-relational databases. Implementing this might be interesting: let
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| 21 | me know if it's useful to you.
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| 22 |
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| 23 | <h3>Does JavaGDBM understand SQL?</h3>
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| 24 |
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| 25 | <p>(Alain Magloire)
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| 26 |
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| 27 | <p>No, JavaGDBM is intended to store on-disk hash tables. They solve
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| 28 | a different class of problem to that appropriate for SQL and
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| 29 | relational databases.
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| 30 |
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| 31 | <h3>What type of database should I use?</h3>
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| 32 |
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| 33 | <p>Broadly, options for data storage in Java include
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| 34 |
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| 35 | <ul>
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| 36 | <li>A hash file through JavaGDBM.
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| 37 | <li>A relational database through JDBC
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| 38 | <li>An object-oriented database
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| 39 | <li>Serialization to a file
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| 40 | </ul>
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| 41 |
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| 42 | <p>Make sure you choose the right tools: there is no single `best' answer.
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| 43 |
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| 44 | <h3>Are you maintaining GDBM?</h3>
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| 45 |
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| 46 | <p>No. I understand that GDBM is still maintained by the FSF.
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| 47 |
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| 48 | <h3>Does it work on NT?</h3>
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| 49 |
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| 50 | <p>It should, but I haven't tried it. You'll need a C compiler to
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| 51 | build the native library. Let me know if you try.
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| 52 |
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| 53 | <h3>Why does the test harness report exceptions</h3>
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| 54 |
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| 55 | <p>The test harness may report messages such as
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| 56 |
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| 57 | <pre>
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| 58 | caught: au.com.pharos.gdbm.GdbmException: File open error: No such file or
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| 59 | directory? (gdbmjava.c:101)
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| 60 | </pre>
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| 61 |
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| 62 | <p>These are expected exceptions: the test harness is making sure that
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| 63 | exceptions are thrown when they should be.
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| 64 |
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| 65 | <h3>I was trying to compile the Java GDBM distribution and it says gdbm.h not found</h3>
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| 66 |
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| 67 | <p>(Sandeep Kumar)
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| 68 |
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| 69 | <ol>
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| 70 | <li>Make sure you have the GDBM library installed on your system.
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| 71 | If the library is not installed, you should be able to find it at
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| 72 | <a href="http://www.gnu.org/">www.gnu.org</a>
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| 73 |
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| 74 | <li>Make sure your compiler is configured to find the libraries and
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| 75 | include files.
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| 76 |
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| 77 | </ol>
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| 78 |
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| 79 | <h3><tt>GdbmFile.h</tt> is missing</h3>
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| 80 |
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| 81 | <p>(Paul Matthews)
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| 82 |
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| 83 | <p><tt>GdbmFile.h</tt> is build by <tt>javah</tt> when the library is
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| 84 | built.
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| 85 |
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| 86 | <h3>What is the best source to learn Java?</h3>
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| 87 |
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| 88 | <p>(Celil Germeyan)
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| 89 |
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| 90 | <p>Personally, I recommend the excellent Java series of books from
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| 91 | <a href="http://www.ora.com/info/java/bibliography.html/">O'Reilly and
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| 92 | Associates</a> and the
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| 93 | <a href="http://java.sun.com/docs/books/index.html">Javasoft/Addison
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| 94 | Wesley</a> books.
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| 95 |
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| 96 | <h3>I get a `not ok 40' message running the test</h3>
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| 97 |
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| 98 | <p>(Steve Waldman)
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| 99 |
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| 100 | <p>If you find a bug, either have a look at the code yourself, or
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| 101 | send e-mail to
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| 102 | <a href="mailto:[email protected]"><tt>[email protected]</tt></a>.
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| 103 | There's no warranty on JavaGDBM, but I will try to respond to your
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| 104 | mail and problem.
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| 105 |
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| 106 | <h3>I get linker errors on Solaris</h3>
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| 107 |
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| 108 | <p>(Alex Soto)
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| 109 |
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| 110 | <pre>
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| 111 | Hi,
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| 112 |
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| 113 | I'm hoping to use your JavaGDBM api for my application, but I'm
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| 114 | having some problems compiling the libgdbmjava.so. Here is a partial
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| 115 | listing of the errors:
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| 116 |
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| 117 | gcc -o libgdbmjava.so -shared gdbmjava.o -lgdbm
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| 118 | Text relocation remains referenced
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| 119 | against symbol offset in file
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| 120 | free 0x258
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| 121 | /usr/local/lib/libgdbm.a(gdbmreorg.o)
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| 122 | free 0xd0
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| 123 | /usr/local/lib/libgdbm.a(gdbmclose.o)
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| 124 | free 0xb8
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| 125 | /usr/local/lib/libgdbm.a(gdbmclose.o)
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| 126 | free 0x218
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| 127 | [snipped]
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| 128 |
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| 129 | I have used the libgdbm.a lib before, and don't believe there is a
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| 130 | problem with it. I'm compiling to Solaris 2.6, using JDK 1.1.4.
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| 131 | </pre>
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| 132 |
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| 133 | <p>The solution turned out to be that the gdbm native library
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| 134 | must be compiled with the <tt>-fpic</tt> flag to cause the compiler to
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| 135 | generate position-independant code.
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| 136 |
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| 137 | <h3>What happens if a reader tries to open the database while a writer is doing something?</h3>
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| 138 |
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| 139 | <p>(Rich Neill)
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| 140 |
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| 141 | <p>Access will be denied until the writer releases its lock.
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| 142 |
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| 143 | <p>JavaGDBM uses a shared-read/exclusive-write protocol at the OS
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| 144 | level. However, multiple Java threads can access a file concurrently.
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| 145 |
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| 146 | <h3>What platforms does JavaGDBM run on?</H3>
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| 147 |
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| 148 | <p>It should run on any platform that supports JDK1.1 or higher, JNI
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| 149 | (Java Native Interface), and GDBM. JavaGDBM is known to run on
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| 150 |
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| 151 | <ul>
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| 152 | <li>Linux/i386
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| 153 | <li>Solaris/SPARC and Solaris/i86
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| 154 | <li>AIX 4
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| 155 | </ul>
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| 156 |
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| 157 | <p>If you have any information on other platforms, please let me know.
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| 158 |
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| 159 | <h3>You don't anticipate going Pure Java soon, do you?</h3>
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| 160 |
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| 161 | <p>(Brian Thorstad)
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| 162 |
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| 163 | <p>It's on the `long-term' TODO list. I'd like to do it, but don't have
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| 164 | any date in mind.
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| 165 |
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| 166 | <h3>Acknowledgements</h3>
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| 167 |
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| 168 | <p>Everybody who's sent in questions or comments.
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| 169 |
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| 170 | <p>Redhat and Javasoft, and the authors of GDBM, Linux, gcc, autoconf,
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| 171 | and other software used in building JavaGDBM.
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| 172 |
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| 173 | </html> |
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