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Spring IoC容器－編碼方式比較

下面會通過一個獲得數據源的例子來比較下傳統編碼模式和IoC編碼模式的不同。首先，在傳統編碼方式下，我們可能這樣獲得數據源并顯示結果：

package?com.lnic.ioc;

import?javax.sql.DataSource;

import?java.sql.Connection;

import?java.sql.Statement;

import?java.sql.ResultSet;

import?java.sql.SQLException;

import?org.apache.commons.dbcp.BasicDataSource;

public?class?BasicDataSourceExample?{

????public?static?void?main(String[]?args)?{

????????DataSource?dataSource?=?setupDataSource();

????????//?創建JDBC數據源

????????Connection?conn?=?null;

????????Statement?stmt?=?null;

????????ResultSet?rset?=?null;

????????try?{

????????????

????????????conn?=?dataSource.getConnection();

????????????stmt?=?conn.createStatement();

????????????rset?=?stmt.executeQuery("select?*?from?user");

????????????System.out.println("Basic?DataSource?executing?results:");

????????????int?numcols?=?rset.getMetaData().getColumnCount();

????????????while?(rset.next())?{

????????????????for?(int?i?=?1;?i?<=?numcols;?i++)?{

????????????????????System.out.print("\t"?+?rset.getString(i));

????????????????}

????????????????System.out.println("");

????????????}

????????}?catch?(SQLException?e)?{

????????????e.printStackTrace();

????????}?finally?{

????????????try?{

????????????????rset.close();

????????????}?catch?(Exception?e)?{

????????????}

????????????try?{

????????????????stmt.close();

????????????}?catch?(Exception?e)?{

????????????}

????????????try?{

????????????????conn.close();

????????????}?catch?(Exception?e)?{

????????????}

????????}

????}

????//?創建數據源

????public?static?DataSource?setupDataSource()?{

????????BasicDataSource?ds?=?new?BasicDataSource();

????????ds.setDriverClassName("com.mysql.jdbc.Driver");

????????ds.setUsername("root");

????????ds.setPassword("131421");

????????ds.setUrl("jdbc:mysql://localhost:3306/test");

????????return?ds;

????}

????//?提示數據源狀態

????public?static?void?printDataSourceStats(DataSource?ds)?throws?SQLException?{

????????BasicDataSource?bds?=?(BasicDataSource)?ds;

????????System.out.println("NumActive:?"?+?bds.getNumActive());

????????System.out.println("NumIdle:?"?+?bds.getNumIdle());

????}

????//?關閉數據源

????public?static?void?shutdownDataSource(DataSource?ds)?throws?SQLException?{

????????BasicDataSource?bds?=?(BasicDataSource)?ds;

????????bds.close();

????}

}

這個累的測試結果顯示：
Basic DataSource executing results:
?123?matthew?YunNanUniversity
?1?lidexian?YunNanUniversity
?2?zhangzili?HunanUniversity

而在Spring 的IoC容器的幫助下我們的編碼會更簡單和靈活。首先，定義個Spring的配置文件：applicationContext.xml。在這個配置文件中，我們配置了三個bean組件，代表不同的數據庫數據源。然后，通過配置jdbcTemplate來啟用需要的具體數據庫數據源。如下：我們采用的MySql數據源。

<?xml?version="1.0"?encoding="UTF-8"?>

<!DOCTYPE?beans?PUBLIC?"-//SPRING//DTD?BEAN//EN"?"http://www.springframework.org/dtd/spring-beans.dtd">

<beans>

????<bean?id="oracle_dataSource"?class="org.apache.commons.dbcp.BasicDataSource"?destroy-method="close">

????????<property?name="driverClassName"?value="oracle.jdbc.driver.OracleDriver"?/>

????????<property?name="url"?value="jdbc:oracle:thin:@localhost:1521:cyberdb"?/>

????????<property?name="username"?value="scott"?/>

????????<property?name="password"?value="tiger"?/>

????</bean>

????

????<bean?id="mysql_dataSource"?class="org.apache.commons.dbcp.BasicDataSource"?destroy-method="close">

????????<property?name="driverClassName"?value="com.mysql.jdbc.Driver"?/>

????????<property?name="url"?value="jdbc:mysql://localhost:3306/test"?/>

????????<property?name="username"?value="root"?/>

????????<property?name="password"?value="131421"?/>

????</bean>

????

????<bean?id="linux_oracle_dataSource"?class="org.apache.commons.dbcp.BasicDataSource"?destroy-method="close">

????????<property?name="driverClassName"?value="oracle.jdbc.driver.OracleDriver"?/>

????????<property?name="url"?value="jdbc:oracle:thin:@192.168.0.3:1521:linuxdb"?/>

????????<property?name="username"?value="scott"?/>

????????<property?name="password"?value="tiger"?/>

????</bean>

????<bean?id="jdbcTemplate"?class="org.springframework.jdbc.core.JdbcTemplate"?lazy-init="true">

????????<property?name="dataSource">

????????????<ref?local="mysql_dataSource"?/>

????????</property>

????</bean>

????

</beans>

然后，如下在代碼中通過載入Spring的配置文件，并初始化bean組件：jdbcTemplate得到數據源，并完成數據查詢。可以看出比傳統的方法簡單和靈活多了，只需要簡單配置即可完成。

package?com.lnic.ioc;

import?java.sql.ResultSet;

import?java.sql.SQLException;

import?java.util.ArrayList;

import?java.util.List;

import?org.springframework.context.ApplicationContext;

import?org.springframework.context.support.ClassPathXmlApplicationContext;

import?org.springframework.jdbc.core.JdbcTemplate;

import?org.springframework.jdbc.core.RowCallbackHandler;

public?class?IocDataSourceExample?{

????public?static?void?main(String[]?args)?{

????????ApplicationContext?ctx?=?new?ClassPathXmlApplicationContext(

????????????????"com/lnic/ioc/applicationContext.xml");//載入spring配置文件applicationContext.xml

????????String?sql?=?"select?*?from?user";

????????JdbcTemplate?jt?=?(JdbcTemplate)?ctx.getBean("jdbcTemplate");//這里采用spring的JdbcTemplate，通過spring的配置文件啟用mysql_dataSource數據源。

????????jt.query(sql,?new?RowCallbackHandler()?{

????????????public?void?processRow(ResultSet?rs)?throws?SQLException?{

????????????????//?do?something?with?the?rowdata?-?like?create?a?new

????????????????//?object?and?add?it?to?the?List?in?the?enclosing?code

????????????????System.out.println("IocDataSource?executing?results:");

????????????????int?numcols?=?rs.getMetaData().getColumnCount();

????????????????

????????????????do?{

????????????????????for?(int?i?=?1;?i?<=?numcols;?i++)?{

????????????????????????System.out.print("\t"?+?rs.getString(i));

????????????????????}

????????????????????System.out.println("");

????????????????}?while?(rs.next());

????????????}

????????});

????}

}

代碼輸出如下：
IocDataSource executing results:
?123?matthew?YunNanUniversity
?1?lidexian?YunNanUniversity
?2?zhangzili?HunanUniversity

posted on 2006-12-26 13:25 matthew 閱讀(457) 評論(0) 編輯收藏所屬分類: JavaEE

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