Spring依赖注入

setter注入

public class BookServiceImpl implements BookService {
    //不要再直接new dao层的对象了!
    private BookDao bookDao;
    
    //提供dao对象进入的入口
    public void setBookDao(BookDao bookDao) {
        this.bookDao = bookDao;
    }
    @Override
    public void bookSave() {
        System.out.println("bookservice save...");
        bookDao.save();
    }
    
}

spring配置文件中需要指定去哪新建注入bean, 以及注入什么bean

    <bean id="bookDao" name="dao booqidao" class="com.itheima.dao.impl.BookDaoImpl"></bean>

    <bean id="bookService" class="com.itheima.service.impl.BookServiceImpl" scope="prototype">
        <property name="bookDao" ref="booqidao"/>
    </bean>

注入基本数据类型: 把ref换成value, 其他相同

构造器注入标准写法

首先预留bean进入的入口(构造方法)

package com.itheima.service.impl;

import com.itheima.dao.BookDao;
import com.itheima.dao.impl.BookDaoImpl;
import com.itheima.service.BookService;

public class BookServiceImpl implements BookService {
    //不要再直接new dao层的对象了!
    private BookDao bookDao;
    
    //构造方法
    public BookServiceImpl(BookDao bookDao) {
        this.bookDao = bookDao;
    }

    @Override
    public void bookSave() {
        System.out.println("bookservice save...");
        bookDao.save();
    }

}

再修改配置文件

    <bean id="bookDao" class="com.itheima.dao.impl.BookDaoImpl"></bean>

    <bean id="bookService" class="com.itheima.service.impl.BookServiceImpl" scope="prototype">
        <constructor-arg name="bookDao" ref="bookDao"/>
    </bean>

基本数据类型就把 ref 改成 value

构造器注入解耦写法

自动装配

最常用的就是byType

<bean id="bookService" class="com.itheima.service.impl.BookServiceImpl" scope="prototype" autowire="byType"/>

还有个byName, 但是bean的id一定要和setter的名字一样, 会造成耦合

<bean id="bookService" class="com.itheima.service.impl.BookServiceImpl" scope="prototype" autowire="byName"/>

集合注入

//首先bean里需要预留setter入口
public class YourClass {
    private List<String> listProperty;
    private Set<String> setProperty;
    private Map<String, String> mapProperty;
    private String[] arrayProperty;

    // Setter方法
    public void setListProperty(List<String> listProperty) {
        this.listProperty = listProperty;
    }

    public void setSetProperty(Set<String> setProperty) {
        this.setProperty = setProperty;
    }

    public void setMapProperty(Map<String, String> mapProperty) {
        this.mapProperty = mapProperty;
    }

    public void setArrayProperty(String[] arrayProperty) {
        this.arrayProperty = arrayProperty;
    }

    // Getter方法（视需要可选）
    public List<String> getListProperty() {
        return listProperty;
    }

    public Set<String> getSetProperty() {
        return setProperty;
    }

    public Map<String, String> getMapProperty() {
        return mapProperty;
    }

    public String[] getArrayProperty() {
        return arrayProperty;
    }
}

<bean id="exampleBean" class="com.example.YourClass">
    <property name="listProperty">
        <list>
            <value>Item 1</value>
            <value>Item 2</value>
            < 3</value>
        </list>
    </property>
</bean>

<bean id="exampleBean" class="com.example.YourClass">
    <property name="setProperty">
        <set>
            <value>Item A>Item B</value>
            <value>Item C</value>
        </set>
    </property>
</bean>

<bean id="exampleBean" class="com.example.YourClass">
    <property name="mapProperty">
        <map>
            <entry key="key1" value="value1" />
            <entry key="key2" value="value2" />
            <entry key="key3" value="value3" />
        </map>
    </property>
</bean>

<bean id="exampleBean" class="com.example.YourClass">
    <property name="arrayProperty">
        <array>
            <value>Element 1</value>
            <value>Element 2</value>
            <value>Element 3</value>
        </array>
    </property>
</bean>

加载properties文件

<?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.xsd">

<!--    解析properties文件-->
    <context:property-placeholder location="classpath*:jdbc.properties"/>

    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="${jdbc.driver}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
    </bean>

</beans>