2.spring框架-----spring framework DI依赖注入

目录

一、DI依赖注入

1.setter注入

 1.1setter引用类型注入 

 1.2setter简单类型注入

2.构造器注入

2.1构造器引用类型注入 

2.2构造器多个引用类型注入 

2.3构造器多个基本类型注入 

---

一、DI依赖注入

Spring提供了两种注入方式，分别是:

setter注入 简单类型 引用类型

构造器注入 简单类型 引用类型

1.setter注入

添加BookDao、BookDaoImpl、UserDao、UserDaoImpl、BookService和 BookServiceImpl类

public interface BookDao {
    public void save();
}
 
public class BookDaoImpl implements BookDao {
    public void save() {
        System.out.println("book dao save ...");
    }
}
 
public interface UserDao {
    public void save();
}
 
public class UserDaoImpl implements UserDao {
    @Override
    public void save() {
        System.out.println("user dao save ...");
    }
}
 
public interface BookService {
    public void save();
}
 
public class BookServiceImpl implements BookService {
    private BookDao bookDao;
 
    public void save() {
        System.out.println("book service save ...");
        bookDao.save();
    }
 
    public void setBookDao(BookDao bookDao) {
        this.bookDao = bookDao;
    }
}

xml文件 

<bean id="bookDao" class="com.itheima.dao.impl.BookDaoImpl"/>
<bean id="bookService" class="com.itheima.service.impl.BookServiceImpl">
<property name="bookDao" ref="bookDao"/>
bean>

运行文件 

public class AppForLifeCycle {
    public static void main( String[] args ) {
        ApplicationContext ctx = new
                ClassPathXmlApplicationContext("applicationContext.xml");
        BookService bookService = (BookService) ctx.getBean("bookService");
        bookService.save();
    }
 
}

 1.1setter引用类型注入 

在BookServiceImpl中声明userDao属性，并提供setter方法

public class BookServiceImpl implements BookService {
    private BookDao bookDao;
    private UserDao userDao;
 
    public void save() {
        System.out.println("book service save ...");
        bookDao.save();
        userDao.save();
    }
 
    public void setBookDao(BookDao bookDao) {
        this.bookDao = bookDao;
    }
 
    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }
}

在applicationContext.xml配置文件中使用property标签注入 

<bean id="bookDao" class="com.itheima.dao.impl.BookDaoImpl"/>
<bean id="userDao" class="com.itheima.dao.impl.UserDaoImpl"/>
<bean id="bookService" class="com.itheima.service.impl.BookServiceImpl">
<property name="bookDao" ref="bookDao"/>
<property name="userDao" ref="userDao"/>
bean>

 1.2setter简单类型注入

1.在BookDaoImpl类中声明对应的简单数据类型的属性

2.为这些属性提供对应的setter方法

3.在applicationContext.xml中配置

在BookDaoImpl类中声明对应的简单数据类型的属性,并提供对应的setter方法

public class BookDaoImpl implements BookDao {
    private String databaseName;
    private int connectionNum;
 
    public void setConnectionNum(int connectionNum) {
        this.connectionNum = connectionNum;
    }
 
    public void setDatabaseName(String databaseName) {
        this.databaseName = databaseName;
    }
    public void save() {
        System.out.println("book dao save..."+databaseName+","+connectionNum);    
    }
}

在applicationContext.xml配置文件中使用property标签注入

  <bean id="bookDao" class="com.itheima.dao.impl.BookDaoImpl">
        <property name="databaseName" value="mysql"/>
        <property name="connectionNum" value="10"/>
    bean>
    <bean id="userDao" class="com.itheima.dao.impl.UserDaoImpl"/>
    <bean id="bookService" class="com.itheima.service.impl.BookServiceImpl">
        <property name="bookDao" ref="bookDao">property>
        <property name="userDao" ref="userDao">property>
    bean>

value:后面跟的是简单数据类型，对于参数类型，Spring在注入的时候会自动转换，但是不能写成英文，spring在将英文转换成int类型的时候就会报错。

引用数据类型使用的是 value=""/>

简单数据类型使用的是 ref=""/>

2.构造器注入

项目中添加BookDao、BookDaoImpl、UserDao、UserDaoImpl、BookService和 BookServiceImpl类

public interface BookDao {
    public void save();
}
 
public class BookDaoImpl implements BookDao {
    private String databaseName;
    private int connectionNum;
 
    public void save() {
        System.out.println("book dao save...");
    }
}
 
public interface UserDao {
    public void save();
}
 
 
public class UserDaoImpl implements UserDao {
    @Override
    public void save() {
        System.out.println("user dao save ...");
    }
}
 
public interface BookService {
    public void save();
}
 
public class BookServiceImpl implements BookService {
    private BookDao bookDao;
 
    public void save() {
        System.out.println("book service save ...");
        bookDao.save();
    }
}

xml文件 

<bean id="bookDao" class="com.itheima.dao.impl.BookDaoImpl"/>
<bean id="bookService" class="com.itheima.service.impl.BookServiceImpl">
<property name="bookDao" ref="bookDao"/>
bean>

运行文件 

public class AppForLifeCycle {
    public static void main( String[] args ) {
        ApplicationContext ctx = new
                ClassPathXmlApplicationContext("applicationContext.xml");
        BookService bookService = (BookService) ctx.getBean("bookService");
        bookService.save();
    }
 
}

2.1构造器引用类型注入 

1.添加带有bookDao参数的构造方法

2.在applicationContext.xml中配置

在BookServiceImpl类中添加带有bookDao参数的构造方法

public class BookServiceImpl implements BookService {
    private BookDao bookDao;
 
    public void save() {
        System.out.println("book service save ...");
        bookDao.save();
    }
 
    public BookServiceImpl(BookDao bookDao) {
        this.bookDao = bookDao;
    }
}

在applicationContext.xml中配置

 

name属性对应的值为构造函数中方法形参的参数名，必须要保持一致。

ref属性指向的是spring的IOC容器中其他bean对象。

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

2.2构造器多个引用类型注入 

在BookServiceImpl声明多个类并提供多个参数的构造函数

public class BookServiceImpl implements BookService {
    private BookDao bookDao;
    private UserDao userDao;
    
    public BookServiceImpl(BookDao bookDao,UserDao userDao) {
        this.bookDao = bookDao;
        this.userDao = userDao;
    }
    
    public void save() {
        System.out.println("book service save ...");
        bookDao.save();
        userDao.save();
    }
}

    <bean id="bookDao" class="com.itheima.dao.impl.BookDaoImpl"/>
    <bean id="userDao" class="com.itheima.dao.impl.UserDaoImpl"/>
    <bean id="bookService" class="com.itheima.service.impl.BookServiceImpl">
        <constructor-arg name="bookDao" ref="bookDao"/>
        <constructor-arg name="userDao" ref="userDao"/>
    bean>

2.3构造器多个基本类型注入 

1.提供一个包含这两个参数的构造方法

2.在applicationContext.xml中进行注入配置

修改BookDaoImpl类，添加构造方法

public class BookDaoImpl implements BookDao {
    private String databaseName;
    private int connectionNum;
    public BookDaoImpl(String databaseName, int connectionNum) {
        this.databaseName = databaseName;
        this.connectionNum = connectionNum;
    }
    public void save() {
        System.out.println("book dao save..."+databaseName+","+connectionNum);
    }
}

在applicationContext.xml中进行注入配置 

    <bean id="bookDao" class="com.itheima.dao.impl.BookDaoImpl">
        <constructor-arg name="databaseName" value="mysql"/>
        <constructor-arg name="connectionNum" value="100"/>
    bean>
    <bean id="userDao" class="com.itheima.dao.impl.UserDaoImpl"/>
    <bean id="bookService" class="com.itheima.service.impl.BookServiceImpl">
        <constructor-arg name="bookDao" ref="bookDao"/>
        <constructor-arg name="userDao" ref="userDao"/>
    bean>

 

当构造函数中方法的参数名发生变化后，配置文件中的name属性也需要跟着变 

方式一:删除name属性，添加type属性，按照类型注入

<bean id="bookDao" class="com.itheima.dao.impl.BookDaoImpl">
<constructor-arg type="int" value="10"/>
<constructor-arg type="java.lang.String" value="mysql"/>
bean>

这种方式可以解决构造函数形参名发生变化带来的耦合问题 但是如果构造方法参数中有类型相同的参数，这种方式就不友好了

方式二:删除type属性，添加index属性，按照索引下标注入，下标从0开始

<bean id="bookDao" class="com.itheima.dao.impl.BookDaoImpl">
<constructor-arg index="1" value="100"/>
<constructor-arg index="0" value="mysql"/>
bean>

这种方式可以解决参数类型重复问题 但是如果构造方法参数顺序发生变化后，这种方式又带来了耦合问题