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Last modified by christoph_lechleitner@iteg_at on 2013-01-31 07.32:56
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1 1  = {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-Preliminary"/}}Preliminary =
2 2  
3 -The SchemaManager and SchemaEngine give you an abstracted access to the database schema of your application, allowing you to add and delete tables, columns, relations and data in the database on application updates. It uses a designated table to keep track of the current schema status, which it will check whenever it is run, and update the database if it is not at the correct version.
3 +The SchemaManager ({{code language="none"}}org.clazzes.jdbc2xml.schema.SchemaManager{{/code}}) and SchemaEngine provide means to maintain the database scheme of an application, allowing you to add and delete tables, columns, relations and data in the database along application updates.
4 4  
5 -SchemaManager ({{code language="none"}}org.clazzes.jdbc2xml.schema.SchemaManager{{/code}}) will create a table called SCHEMA_HISTORY if it can not find it the first time it is run. This table contains the following columns:
5 +=== {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-SchemaHistoryTable"/}}Schema History Table ===
6 6  
7 -{{code language="none"}}
8 -VERSION:varchar(10), not null, primary key
9 -DESCRIPTION:varchar(512), nullable
10 -CREATION_DATE:date, nullable
11 -SERIALNR:integer(5), not null
12 -{{/code}}
7 +A designated schema table, by default named SCHEMA_HISTORY, is used to keep track of the current scheme. It will be automatically at SchemaManager's first run. (% style="font-size: 10.0pt;line-height: 13.0pt;" %)SCHEMA_HISTORY contains the following columns:
13 13  
9 +|=(((
10 +
11 +)))|=(((
12 +
13 +)))
14 +|(((
15 +(% class="code" %)
16 +(((
17 +VERSION
18 +)))
19 +)))|(((
20 +(% class="code" %)
21 +(((
22 +varchar(10), not null, primary key
23 +)))
24 +)))
25 +|(((
26 +(% class="code" %)
27 +(((
28 +DESCRIPTION
29 +)))
30 +)))|(((
31 +(% class="code" %)
32 +(((
33 +varchar(512), nullable
34 +)))
35 +)))
36 +|(((
37 +(% class="code" %)
38 +(((
39 +CREATION_DATE
40 +)))
41 +)))|(((
42 +(% class="code" %)
43 +(((
44 +date, nullable
45 +)))
46 +)))
47 +|(((
48 +(% class="code" %)
49 +(((
50 +SERIALNR
51 +)))
52 +)))|(((
53 +(% class="code" %)
54 +(((
55 +integer(5), not null
56 +)))
57 +)))
58 +
59 +=== {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-CustomnameforSchemaHistoryTable"/}}Custom name for Schema History Table ===
60 +
61 +(% style="font-size: 10.0pt;line-height: 13.0pt;" %)In (% style="font-size: 10.0pt;font-weight: normal;line-height: 13.0pt;" %)heterogenous environments as well as in heavily modularized software architectures a single database may be shared by multiple parties each requiring a couple of tables.
62 +
63 +(% style="font-size: 10.0pt;font-weight: normal;line-height: 13.0pt;" %)To allow multiple modules (applications, libraries, other OSGi bundles) to use (% style="font-size: 10.0pt;line-height: 13.0pt;" %)JDBC2XML's SchemaManager concurrently within one database, as of JDBC 1.1.1 SchemaManager hold the name of the schema history table in an overwritable property, {{code language="none"}}versionHistoryTable{{/code}}. See (%%)[[JDBCTOXML-11>>url:https://jira.clazzes.org/browse/JDBCTOXML-11||shape="rect"]](% style="font-size: 10.0pt;line-height: 13.0pt;" %).
64 +
14 14  = {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-ProjectConfiguration"/}}Project Configuration =
15 15  
16 -To function correctly, SchemaManager needs a DataSource ({{code language="none"}}javax.sql.DataSource{{/code}}) and a list of TableInfo ({{code language="none"}}org.clazzes.jdbc2xml.schema.TableInfo{{/code}}) Objects, from which a database will be created if it finds an empty database. To function properly, it also needs an implementation of ISchemaEngine ({{code language="none"}}org.clazzes.jdbc2xml.schema.ISchemaEngine{{/code}}).
67 +SchemaManager requires a DataSource ({{code language="none"}}javax.sql.DataSource{{/code}}) and a list of TableInfo ({{code language="none"}}org.clazzes.jdbc2xml.schema.TableInfo{{/code}}) Objects, from which database structures will be created if an "empty" database is detected. Furthermore, an implementation of ISchemaEngine ({{code language="none"}}org.clazzes.jdbc2xml.schema.ISchemaEngine{{/code}}) is required.
17 17  
18 -Optionally, you may set the base version (default value 0.1.00) and base description String (default "initial database schema").
69 +Optionally, a base version (default value 0.1.00) and a base description String (default "initial database schema") may be specified.
19 19  
20 20  Database updates are passed as a Map<String, ISchemaUpdateSnippet> (org.clazzes.jdbc2xml.schema.ISchemaUpdateSnippet) - details see below.
21 21  
22 22  To perform the operations, call {{code language="none"}}SchemaManager.start(){{/code}}.
23 23  
24 -=== {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-UsingSpringorOSGi/Blueprint"/}}Using Spring or OSGi/Blueprint ===
75 +=== {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-ConfigurationusingSpringorOSGi/Blueprint"/}}Configuration using Spring or OSGi/Blueprint ===
25 25  
26 26  If you are using OSGi with Blueprint or Spring to set up your project, you can configure a SchemaManager instance by adding the following to your blueprint {{code language="none"}}services.xml{{/code}} (or Spring configuration file):
27 27  
... ... @@ -33,7 +33,7 @@
33 33  </bp:reference>
34 34   
35 35  <bp:bean id="sqlDialect" factory-ref="dialectFactory" factory-method="newDialect">
36 -<bp:argument> <!-- Pass JDBC URL as an argument -->
87 +<bp:argument ref="jdbcUrl"><!-- bean jdbcUrl specified above -->
37 37  </bp:argument>
38 38  </bp:bean>
39 39   
... ... @@ -45,22 +45,35 @@
45 45  <bp:bean id="databaseSetup" class="org.clazzes.jdbc2xml.schema.SchemaManager" init-method="start">
46 46  <bp:property name="dataSource" ref="dataSource"></bp:property>
47 47  <bp:property name="schemaEngine" ref="schemaEngine"></bp:property>
99 + <!-- optional but recommended: special name for schema history table: -->
100 + <bp:property name="versionHistoryTable" value="MYLIB_SCHEMA_HISTORY"/>
101 + <!-- optional but recommended: explicit first version -->
48 48  <bp:property name="baseVersion" value="0.1.00" />
49 49  <bp:property name="baseTables">
50 -<!-- Add List of TableDefinitions here -->
104 +<!-- List of TableDefinitions here (see below), typical: -->
105 + <!-- <bp:bean factory-ref="tableDefinitions" factory-method="getSetup" /> -->
51 51  </bp:property>
107 + <!-- Add Update-Snippets here, example for updates from 0.1.00 to 0.1.01 and on to 0.2.00
52 52  <bp:property name="upateSnippets">
53 -<!-- Add Update-Snippets here -->
109 +<bp:map>
110 + <bp:entry key="0.1.00" value="foo.schema.SchemaUpdate_0_1_01"></bp:entry>
111 + <bp:entry key="0.1.01" value="foo.schema.SchemaUpdate_0_2_00"></bp:entry>
112 +</bp:map>
54 54  </bp:property>
114 + -->
55 55  </bp:bean>
56 56  {{/code}}
57 57  
58 -By default, JDBC2XML provides an implementation of IDialectFactory and ISchemaEngineFactory as an OSGi service or via ServiceRegistry lookup for Spring.
118 +By default, JDBC2XML provides an implementation of IDialectFactory and ISchemaEngineFactory as an OSGi service or via ServiceRegistry for Spring.
59 59  
60 60  = {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-Settingupaninitialdatabaseschema"/}}Setting up an initial database schema =
61 61  
62 -To create an initial database schema, you will need to provide SchemaManager with a list of TableInfo objects. The recommended way to do this is to provide a class in your project which creates this list in it's constructor and provides it through a getter. You can instantiate this class in your Spring/Blueprint config as a singleton, and feed the provided List to SchemaManager. An example of this class could look like this:
122 +To create an initial database schema, SchemaManager needs a list of TableInfo objects.
63 63  
124 +The recommended strategy is to create an InitialSchema class providing this list through a getter.
125 +
126 +(% style="font-size: 10.0pt;line-height: 13.0pt;" %)This is an example:
127 +
64 64  {{code language="java"}}
65 65  package org.clazzes.example.jdbc2xml;
66 66  
... ... @@ -73,77 +73,227 @@
73 73  import org.clazzes.jdbc2xml.schema.PrimaryKeyInfo;
74 74  import org.clazzes.jdbc2xml.schema.TableInfo;
75 75   
76 -public class TableDefinitions {
140 +public class InitialSchema {
77 77  
78 - /* It is adviseable to provide the Strings used as names for tables and columns as
79 - constants, so they can be reused to build sql-statements */
80 - public static final String TB_EXAMPLE_TABLE_NAME = "ADDRESSBOOK";
81 - public static final String COL_EXAMPLE_ID = "ID";
82 - public static final String COL_EXAMPLE_NAME = "NAME";
83 - public static final String COL_EXAMPLE_ADDRESS_REF = "ADDRESS";
84 - public static final String COL_EXAMPLE_BIRTHDAY = "BIRTHDAY";
85 - 
86 - /* ... */
87 - 
88 88   private List<TableInfo> setup;
89 89  
90 90   public TableDefinitions() {
91 -/* Create a table */
92 -TableInfo exampleTable = new TableInfo(TB_EXAMPLE_TABLE_NAME);
145 +// Create a table
146 +TableInfo exampleTable = new TableInfo(TableDefs.TB_EXAMPLE_TABLE_NAME);
93 93  exampleTable.setColumns(
94 94   Arrays.asList(new ColumnInfo[] {
95 -new ColumnInfo(COL_EXAMPLE_ID, Types.BIGINT, 20, null, false, null,true),
96 -new ColumnInfo(COL_EXAMPLE_NAME, Types.VARCHAR, 256, null, false, null),
97 -new ColumnInfo(COL_EXAMPLE_ADDRESS_REF, Types.BIGINT, 20, null, true, null),
98 -new ColumnInfo(COL_EXAMPLE_BIRTHDAY, Types.DATE, 12, null, false, null)
149 +new ColumnInfo(TableDefs.COL_EXAMPLE_ID, Types.BIGINT, 20, null, false, null,true),
150 +new ColumnInfo(TableDefs.COL_EXAMPLE_NAME, Types.VARCHAR, 256, null, false, null),
151 +new ColumnInfo(TableDefs.COL_EXAMPLE_ADDRESS_REF, Types.BIGINT, 20, null, true, null),
152 +new ColumnInfo(TableDefs.COL_EXAMPLE_BIRTHDAY, Types.DATE, 12, null, false, null)
99 99  }));
100 100   
101 -/* Example for creating a foreign key reference */
155 +// Example for creating a foreign key reference
102 102  exampleTable.setForeignKeys(Arrays.asList(new ForeignKeyInfo[] {
103 103  new ForeignKeyInfo("FK_EXAMPLE_ADDRESS", COL_EXAMPLE_ADDRESS_REF, TB_ADDRESS, COL_ADDRESS_ID)
104 104  }));
105 105   
106 -/* Example for creating a primary key */
160 +// Example for creating a primary key
107 107  exampleTable.setPrimaryKey(
108 108  new PrimaryKeyInfo("PK_EXAMPLE", COL_EXAMPLE_ID)
109 109  );
110 110  
111 -/* ... */
165 +// ...
112 112   
113 113  this.setup = Arrays.asList(
114 114  exampleTable,
115 -/* ... */
169 +// ...
116 116  );
117 117  
118 118   }
119 119    
120 - public List<TableInfo> getSetup() {
121 -return this.setup;
174 + public List<TableInfo> getSchema() {
175 +return this.schema;
122 122   }
123 123  
124 124  }
125 125  {{/code}}
126 126  
181 +{{code language="java"}}
182 +package org.clazzes.example.jdbc2xml;
183 +
184 +import java.sql.Types;
185 +import java.util.Arrays;
186 +import java.util.List;
187 +
188 +import org.clazzes.jdbc2xml.schema.ColumnInfo;
189 +import org.clazzes.jdbc2xml.schema.ForeignKeyInfo;
190 +import org.clazzes.jdbc2xml.schema.PrimaryKeyInfo;
191 +import org.clazzes.jdbc2xml.schema.TableInfo;
192 +
193 +public class TableDefs {
194 +
195 + // It is adviseable to provide the Strings used as names for tables and columns as constants,
196 + // so they can be reused savely to construct SQL statements
197 + public static final String TABLENAME_ADDRESSBOOK = "ADDRESSBOOK";
198 + public static final String COL_ADDRESSBOOK_ID = "ID";
199 + public static final String COL_ADDRESSBOOK_NAME = "NAME";
200 + public static final String COL_ADDRESSBOOK_ADDRESS_REF = "ADDRESS";
201 + public static final String COL_ADDRESSBOOK_BIRTHDAY = "BIRTHDAY";
202 +
203 +}
204 +{{/code}}
205 +
206 +
207 +
208 +
209 +
127 127  You must inject {{code language="none"}}TableDefinitions.getSetup(){{/code}} into {{code language="none"}}SchemaManager.setBaseTables(){{/code}} before calling {{code language="none"}}SchemaManager.start(){{/code}}.
128 128  
129 -Using Blueprint/Spring, you can do this with the following snippet:
212 +Using Blueprint/Spring, you can do this by inserting the following snippet in the bean definition for SchemaManager:
130 130  
131 -{{code language="none"}}
132 - 
214 +{{code language="html/xml"}}
215 +<!-- SchemaManager bean definition starts here ... -->
216 +<bp:property name="baseTables">
217 +<bp:bean factory-ref="tableDefinitions" factory-method="getSetup" />
218 +</bp:property>
219 +<!-- ... and continues here -->
133 133  {{/code}}
134 134  
135 -= {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-UpdatingadatabaseschemawithSchemaUpdateSnippets"/}}Updating a database schema with SchemaUpdateSnippets =
222 += {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-UpdatingadatabaseschemawithISchemaUpdateSnippet"/}}Updating a database schema with ISchemaUpdateSnippet =
136 136  
137 137  To update the database or it's content with schema updates, you must create a new implementation of ISchemaUpdateSnippet ({{code language="none"}}org.clazzes.jdbc2xml.schema.ISchemaUpdateSnippet{{/code}}) for each consecutive update. SchemaManager takes a {{code language="none"}}Map<String, Class<? extends ISchemaUpdateSnippet>>{{/code}} which contains the update classes keyed by the originating (e.g. previous) version.
138 138  
139 -
226 +An example for an implementation of a schema update snippet could look like this:
140 140  
141 -
228 +{{code language="java"}}
229 +package org.clazzes.example.jdbc2xml.updates;
142 142  
143 -
231 +import java.sql.SQLException;
232 +import java.sql.Types;
233 +import java.util.Arrays;
234 +import org.clazzes.jdbc2xml.schema.ColumnInfo;
235 +import org.clazzes.jdbc2xml.schema.ISchemaEngine;
236 +import org.clazzes.jdbc2xml.schema.ISchemaUpdateSnippet;
237 +import org.clazzes.jdbc2xml.schema.PrimaryKeyInfo;
238 +import org.clazzes.jdbc2xml.schema.TableInfo;
144 144  
145 -
240 +public class SchemaUpdate0_1_01 implements ISchemaUpdateSnippet {
241 + 
242 +// This is only accessed through the getter
243 +private static final String TARGET_VERSION = "0.1.01";
244 + 
245 +// Here it is also adviseable to define constants for reuse in statements.
246 +public static final String COL_EXAMPLE_GENDER = "GENDER";
146 146  
248 +
249 +@Override
250 +public String getTargetVersion() {
251 +return TARGET_VERSION;
252 +}
253 +
254 +@Override
255 +public String getUpdateComment() {
256 +return "Adding column "+COL_EXAMPLE_GENDER+" to table "+TableDefinitions.TB_EXAMPLE_TABLE_NAME+".";
257 +}
258 +
259 +@Override
260 +public void performUpdate(ISchemaEngine schemaEngine) throws SQLException {
261 +TableInfo ti = schemaEngine.fetchTableInfo(TableDefinitions.TB_EXAMPLE_TABLE_NAME, null);
262 + schemaEngine.addColumn(ti, new ColumnInfo(COL_EXAMPLE_GENDER, Types.VARCHAR, 1, null, true, null));
263 +}
264 +}
265 +
266 +
267 +{{/code}}
268 +
269 +The return values of {{code language="none"}}ISchemaUpdateSnippet.getTargetVersion(){{/code}} and {{code language="none"}}ISchemaUpdateSnippet.getUpdateComment(){{/code}} are written to the {{code language="none"}}SCHEMA_HISTORY{{/code}} table. The update itself is performed in {{code language="none"}}ISchemaUpdateSnippet.performUpdate(){{/code}}. In the above example, it adds a column called {{code language="none"}}GENDER{{/code}} to the example table created by the TableDefinitions class above.
270 +
271 +To add an entire table you would use the {{code language="none"}}ISchemaEngine.createTable(){{/code}} method, like this:
272 +
273 +{{code language="java"}}
274 +@Override
275 +public void performUpdate(ISchemaEngine schemaEngine) throws SQLException {
276 + TableInfo tiGroup = new TableInfo(TB_GROUP);
277 + tiGroup.setColumns(Arrays.asList(new ColumnInfo[] {
278 + new ColumnInfo(TableDefinitions.COL_ID, Types.VARCHAR, 36, null, false, null),
279 + new ColumnInfo(TableDefinitions.COL_NAME, Types.VARCHAR, 100, null, false, null),
280 + new ColumnInfo(TableDefinitions.COL_DESCRIPTION, Types.VARCHAR, 512, null, true, null)
281 + }));
282 + tiGroup.setPrimaryKey(new PrimaryKeyInfo(PK_GROUP, TableDefinitions.COL_ID));
283 + tiGroup.setIndices(Arrays.asList(new IndexInfo(IDX_GROUP_01, TableDefinitions.COL_NAME, true, null)));
284 +
285 +schemaEngine.createTable(tiGroup, true);
286 +}
287 +{{/code}}
288 +
289 +Executing a PreparedStatement also works, using ISchemaEngine.getConnection() to retrieve the database connection:
290 +
291 +{{code language="java"}}
292 +@Override
293 +public void performUpdate(ISchemaEngine schemaEngine) throws SQLException {
294 + String sql = "UPDATE "+TableDefinitions.TB_EXAMPLE_TABLE_NAME+" SET "+TableDefinitions.COL_EXAMPLE_NAME+"=?";
295 +
296 + PreparedStatement ps = schemaEngine.getConnection().prepareStatement(sql);
297 +
298 + ps.setNull(1, Types.VARCHAR);
299 +
300 + ps.execute();
301 +}
302 +{{/code}}
303 +
304 +To create the map of updates in Blueprint/Spring and inject them into SchemaManager, use the following xml-Snippet:
305 +
306 +{{code language="html/xml"}}
307 +<!-- SchemaManager bean definition starts here ... -->
308 +<bp:property name="upateSnippets">
309 +<bp:map>
310 +<bp:entry key="0.1.00" value="org.clazzes.example.jdbc2xml.updates.SchemaUpdate0_1_01"></bp:entry>
311 +<!-- more entries come here: "key" is the schema version to update, "value" the qualified classname of the schema update -->
312 +</bp:map>
313 +</bp:property>
314 +<!-- ... and continues here -->
315 +{{/code}}
316 +
317 += {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-SchemaMaintainanceStrategies"/}}Schema Maintainance Strategies =
318 +
319 +The JDBC2XML Schema management tools allow for 2 different strategies:
320 +
321 +=== {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-Frozen(Initial)TableList"/}}Frozen (% style="font-size: 14.0pt;" %)(Initial) Table List(%%) ===
322 +
323 +The legacy strategy is:
324 +
325 +(% style="list-style-type: square;" %)
326 +* At the start of a project, create and use TableDefinitions.java
327 +* After the first commit, TableDefinitions are considered frozen, all changes go into SchemaUpdates, up to one update per source code commit
328 +
329 +Advantage: Rock solid.
330 +
331 +Disadvantage: No place to look for the complete current scheme, except actual databases. See //Recommendation 1// below for a workaround.
332 +
333 +=== {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-Possiblebutdangerous:Evolving(Initial)TableList"/}}Possible but dangerous: Evolving (Initial) Table List ===
334 +
335 +To keep the TableDefinitions up do date, one might use this strategy:
336 +
337 +(% style="list-style-type: square;" %)
338 +* keep the TableDefinitions up to date, so an empty database always gets the current scheme in one shot
339 +* SchemaUpdates are only applied to existing databases
340 +
341 +Advantage: Immediate overview over current scheme.
342 +
343 +Disadvantage: Very real danger of messing something up, because
344 +
345 +(% style="list-style-type: square;" %)
346 +* schema updates have to be coded in 2 different places in 2 different ways
347 +* the bean definition has to be maintained in 2 places but just 1
348 +
349 +Conclusion: DO NOT DO THIS. This strategy may be ok in very early stages, but at some point it has to be
350 +
351 +=== {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-Recommendation1:SplitTableDefinitionsfrominitialTableList"/}}Recommendation 1: Split TableDefinitions from initial Table List ===
352 +
353 +If TableDefinitions (pseudo constants for table and column names) go in a dedicated pseudo class it can serve as good overview over the database structure.
354 +
355 +=== {{id name="HowTocreateandupdateDatabasesusingSchemaManagerandSchemaUpdateSnippets-Recommendation2:FreezeTableDefinition,notafterRC/1.0/GA"/}}Recommendation 2: (% style="font-size: 14.0pt;" %)Freeze Table Definition, not after RC/1.0/GA(%%) ===
356 +
357 +It may be ok to start a new project using a fast changing (% style="font-size: 10.0pt;line-height: 13.0pt;" %)(Initial) Table List.
358 +
359 +(% style="font-size: 10.0pt;line-height: 13.0pt;" %)But, please, freeze it at some point. Once the first test server is setup up, internally or at a friendly customer, the Frozen Initial Table List Strategy is the only valid one!
360 +
147 147  
148 148  
149 149  
Confluence.Code.ConfluencePageClass[0]
Id
... ... @@ -1,1 +1,1 @@
1 -656809
1 +656817
URL
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1 -https://clazzes.atlassian.net/wiki/spaces/JDBC2XML/pages/656809/How To create and update Databases using SchemaManager and SchemaUpdateSnippets
1 +https://clazzes.atlassian.net/wiki/spaces/JDBC2XML/pages/656817/How To create and update Databases using SchemaManager and SchemaUpdateSnippets