Spring4 Learning: Using external properties files

When configuring beans in a configuration file, it is sometimes necessary to mix the details of the system deployment in the bean's configuration (for example: file path, data source configuration information, etc.) and these deployment details actually need to be separated from the bean configuration;

Spring provides a propertyplaceholderconfigurer Beanfactory post processor that allows the user to move the contents of the bean configuration to a property file, which can be used in the bean configuration file in the form of ${var} variables, propertyplaceholderconfigurer dependent files, and use these attributes to replace attribute variables;

Spring also allows the use of ${propname} in property files to implement mutual references between attributes.

Example:

1. Import the jar package for the C3P0 data source and the driver jar package for MySQL;

2. Writing Beans-properties.xml

<?xml version= "1.0"  encoding= "UTF-8"? ><beans xmlns= "http://www.springframework.org/ Schema/beans "    xmlns:xsi=" Http://www.w3.org/2001/XMLSchema-instance "     xmlns:context= "Http://www.springframework.org/schema/context"     xsi:schemalocation= "Http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd         http://www.springframework.org/schema/context http:// Www.springframework.org/schema/context/spring-context-4.0.xsd ">         <!--  Import Properties File  -->    <context:property-placeholder location= " Classpath:db.properties "/>        <bean id=" DataSource "  class= "Com.mchange.v2.c3p0.ComboPooledDataSource" >    <!--        &nbsP; <property name= "User"  value= "root" ></property>         <property name= "Password"  value= "root" ></property>         <property name= "Driverclass"  value= "Com.mysql.jdbc.Driver" ></ Property>        <property name= "JdbcUrl"  value= "JDBC: Mysql:///test "></property>     -->         <!--  Using properties of an extern properties file  -->            <property name= "User"  value= "${user}" ></property>         <property name= "Password"  value= "${password}" ></property>         <property name= "Driverclass"  value= "${driverclass}" ></ property>  &Nbsp;     <property name= "Jdbcurl"  value= "${jdbcurl}" ></property >            </bean></beans>

3. Writing the external properties file db.properties

User=rootpassword=rootdriverclass=com.mysql.jdbc.driverjdbcurl=jdbc:mysql:///test

4. Writing Main.java

Package Com.ksk.spring.beans.scope;import Java.sql.sqlexception;import Javax.sql.datasource;import Org.springframework.context.applicationcontext;import Org.springframework.context.support.classpathxmlapplicationcontext;import Com.ksk.spring.car;public class Main {PU Blic static void Main (string[] args) throws SQLException {ApplicationContext ctx = new Classpathxmlapplicationcont        Ext ("Beans-properties.xml");        DataSource DataSource = (DataSource) ctx.getbean ("DataSource");    System.out.println (Datasource.getconnection ()); }}

Spring4 Learning: Using external properties files