Spring IoC容器-编码方式比较

    技术2022-05-11  19

    下面会通过一个获得数据源的例子来比较下传统编码模式和IoC编码模式的不同。首先,在传统编码方式下,我们可能这样获得数据源并显示结果: 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();        // 创建JDBC数据源        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) {            }        }    }    // 创建数据源    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;    }    // 提示数据源状态    public static void printDataSourceStats(DataSource ds) throws SQLException {        BasicDataSource bds = (BasicDataSource) ds;        System.out.println("NumActive: " + bds.getNumActive());        System.out.println("NumIdle: " + bds.getNumIdle());    }    // 关闭数据源    public static void shutdownDataSource(DataSource ds) throws SQLException {        BasicDataSource bds = (BasicDataSource) ds;        bds.close();    }} 这个累的测试结果显示: Basic DataSource executing results:  123 matthew YunNanUniversity  1 lidexian YunNanUniversity  2 zhangzili HunanUniversity 而在Spring 的IoC容器的帮助下我们的编码会更简单和灵活。首先,定义个Spring的配置文件:applicationContext.xml。在这个配置文件中,我们配置了三个bean组件,代表不同的数据库数据源。然后,通过配置jdbcTemplate来启用需要的具体数据库数据源。如下:我们采用的MySql数据源。 <? 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,如下在代码中通过载入Spring的配置文件,并初始化bean组件:jdbcTemplate得到数据源,并完成数据查询。可以看出比传统的方法简单和灵活多了,只需要简单配置即可完成。 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");//载入spring配置文件applicationContext.xml        String sql = "select * from user";        JdbcTemplate jt = (JdbcTemplate) ctx.getBean("jdbcTemplate");//这里采用spring的JdbcTemplate,通过spring的配置文件启用mysql_dataSource数据源。        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());            }        });    }} 代码输出如下: IocDataSource executing results:  123 matthew YunNanUniversity  1 lidexian YunNanUniversity  2 zhangzili HunanUniversity  

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