Spring之引入外部的属性配置文件

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前言

将信息单独写到一个属性配置文件中，这样用户修改起来会更加方便

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一、引入外部的属性配置文件

1.1、写一个数据源类

MyDataSource：

public class MyDataSource implements DataSource {
    private String driver;
    private String url;
    private String username;
    private String password;

    public void setDriver(String driver) {
        this.driver = driver;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "MyDataSource{" +
                "driver='" + driver + '\'' +
                ", url='" + url + '\'' +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }

    public MyDataSource() {
        super();
    }

    @Override
    public int hashCode() {
        return super.hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        return super.equals(obj);
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

    @Override
    protected void finalize() throws Throwable {
        super.finalize();
    }

    @Override
    public Connection getConnection() throws SQLException {
        return null;
    }

    @Override
    public Connection getConnection(String username, String password) throws SQLException {
        return null;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        return false;
    }

    @Override
    public PrintWriter getLogWriter() throws SQLException {
        return null;
    }

    @Override
    public void setLogWriter(PrintWriter out) throws SQLException {

    }

    @Override
    public void setLoginTimeout(int seconds) throws SQLException {

    }

    @Override
    public int getLoginTimeout() throws SQLException {
        return 0;
    }

    @Override
    public Logger getParentLogger() throws SQLFeatureNotSupportedException {
        return null;
    }
}
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1.2、写spring配置文件

    引入外部的properties文件
        第一步：引入context命名空间 xmlns:context="http://www.springframework.org/schema/context"
        第二步：使用标签的location属性来指定属性配置文件的路径
    配置数据源：一般会使用${jdbc.username} 而不是直接${username}，会有一点小bug，会调用到系统的username：Adminstrator
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<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 https://www.springframework.org/schema/context/spring-context.xsd">
    
    <context:property-placeholder location="db.properties">context:property-placeholder>

    
    <bean id="dataSourceBean" class="com.powernode.spring6.bean.MyDataSource">
        <property name="driver" value="${jdbc.driver}">property>
        <property name="url" value="${jdbc.url}">property>
        <property name="username" value="${jdbc.username}">property>
        <property name="password" value="${jabc.password}">property>
    bean>
beans>
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1.3、写测试程序

    @Test
    public void testProperties(){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-properties.xml");
        MyDataSource ds = applicationContext.getBean("dataSourceBean", MyDataSource.class);
        System.out.println(ds);
    }
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1.4、运行结果

运行结果