[小结]Java数据库连接 - 配置 Struts 数据源
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7.配置 Struts 数据源
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一般步骤:
7.1配置JNDI数据源
在struts-config.xml配置文件<struts-config>标签下加入类似如下配置内容
<data-source>属性type用来定义数据源javax.sql.DataSource实现类:org.apache.commons.dbcp.BasicDataSource
<set-property>标签各属性设置可参考实现类:org.apache.commons.dbcp.BasicDataSource中各数据库连接相关属性的定义.<set-property>的作用就是根据实现类中的setXXX()方法,设置其内容.这就好像<jsp:setProperty>用来设置bean属性一样.
??? <data-sources>
?????? <data-source type="org.apache.commons.dbcp.BasicDataSource">
?????????? <set-property property="driverClassName" value="com.mysql.jdbc.Driver" />
?????????? <set-property property="url" value="jdbc:mysql://localhost:3306/mydb"/>
?????????? <set-property property="username" value="root"/>
?????????? <set-property property="password" value="root"/>
?????????? <set-property property="maxActive" value="30"/>
?????????? <set-property property="maxIdle" value="10"/>
?????????? <set-property property="maxWait" value="1000"/>
?????? </data-source>
??? </data-sources>
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7.2获取数据源实例
通过org.apache.struts.action.Action类中定义的二个方法:
protected DataSource getDataSource(HttpServletRequest request, String key)
protected DataSource getDataSource(HttpServletRequest request)
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关键代码:
??? DataSource ds = this.getDataSource(request);?
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查看org.apache.struts.action.Action类源代码:
??? /**
???? * <p>Return the specified data source for the current module.</p>
???? *
???? * @param request The servlet request we are processing
???? * @param key???? The key specified in the <code><data-sources></code>
???? *??????????????? element.
???? *
???? * @since Struts 1.1
???? */
??? protected DataSource getDataSource(HttpServletRequest request, Stringkey) {
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??????? // Identify the current module
??????? ServletContext context =getServlet().getServletContext();
??????? ModuleConfig moduleConfig =
??????????? ModuleUtils.getInstance().getModuleConfig(request,context);
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??????? return (DataSource)context.getAttribute(key + moduleConfig.getPrefix());
??? }
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??? protected DataSourcegetDataSource(HttpServletRequest request) {
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??????? return (getDataSource(request,Globals.DATA_SOURCE_KEY));
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??? }
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由此可知,数据源需要在自定义的Action处理类(继承自Action)中获取数据源.
参数说明:
request??? 一次用户请求
key??? <data-source>标签设置的key属性.未设置key属性时,默认值为Globals.DATA_SOURCE_KEY
?????? 通过protected DataSource getDataSource(HttpServletRequest request)方法获取数据源
?????? 默认调用key值为Globals.DATA_SOURCE_KEY的数据源
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引用自struts-config_1_2.dtd
???? key???????????? Servlet context attributekey under which this data source
???????????????????? will be stored.? Default is the value specified by string
???????????????????? constant defined byGlobals.DATA_SOURCE_KEY. The application
???????????????????? module prefix (if any) isappended to the key
???????????????????? (${key}$prefix}).
????????????????????[org.apache.struts.Globals.DATA_SOURCE_KEY]
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注: 该方法权限是protected,因为可以在不同包的子类中使用,无法在不同包非子类中被调用.另外,自定义的Action处理类构造函数只在第一次请求时,被调用.因此,自定义的Action处理类的实例化很可能用到单例模式.
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7.3数据库操作
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一般步骤:
a) 通过数据源实例建立数据库连接
b) 创建Statement对象
c) 获取结果集
d) 关闭数据库连接资源(包括ResultSet,Statement,Connection实例)
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关键代码:
??? Connection conn = ds.getConnection();
??? PreparedStatement stmt = conn.prepareStatement(sql);
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??? stmt.setString(1, username);
??? stmt.setString(2, password);
??? ResultSet rs = stmt.executeQuery();
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??? if(rs.next())
??? {
?????? request.setAttribute("hint", bundle.getString("login.check.hint.success"));
?????? return mapping.findForward("success");
??? }
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