Spring（Spring的读取外部资源- p 命名空间）

Spring读取外部资源

实际开发中，数据库的资源一般会单独保存起来。一般会保存到后缀为properties的文件中，方便维护和修改，如果Spring加载资源,就需要在spring.xml中读取properties中的资源

xxx.properties

user=root
password=root
url = jdbc:mysql://localhost:3306/library
driverName=com.mysql.cj.jdbc.Driver

spring-xx.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 https://www.springframework.org/schema/context/spring-context.xsd">
<!--    导入外部资源-->
    <context:property-placeholder location="classpath:jdbc.properties"></context:property-placeholder>
<!--SpringEL-->
    <bean id="dataSource" class="com.southwind.entity.DataSouse ">
        <property name="user" value="${user}"></property>
        <property name="password" value="${password}"></property>
        <property name="url" value="${url}"></property>
        <property name="driverName" value="${driverName}"></property>
    </bean>
</beans>

DataSource:

package com.southwind.entity;

import lombok.Data;

@Data
public class DataSouse {
    private String user;
    private String password;
    private String url;
    private String driverName;
}

测试类：

package com.southwind.test;

import com.southwind.entity.DataSouse;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test4 {
    public static void main(String[] args) {
        ApplicationContext applicationContext =new ClassPathXmlApplicationContext("spring-property.xml");
        DataSouse dataSouse = (DataSouse)applicationContext.getBean("dataSource");
        System.out.println(dataSouse);
    }
}

Spring p 命名空间

p 命名空间简化Bean的配置

Spring-p.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:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="student" class="com.southwind.entity.Student" p:id="1" p:name="张三"></bean>
</beans>

测试类：

package com.southwind.test;

import com.southwind.entity.Student;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test5 {
    public static void main(String[] args) {
        ApplicationContext applicationContext =new ClassPathXmlApplicationContext("spring-p.xml");
        Student student = (Student)applicationContext.getBean("student");
        System.out.println(student);
    }
}

如果和级联一样：也是p:age-ref=""写类

同时也要引入：

xmlns:p="http://www.springframework.org/schema/p"

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">