在本知识点中,将演示如何使用注解的方式完成注入对象中的效果
步骤1:先运行,看到效果,再学习
步骤2:模仿和排错
步骤3:修改applicationContext.xml
步骤4:@Autowired
步骤5:运行测试
步骤6:@Autowired的位置
步骤7:@Resource
步骤8:对Bean的注解
步骤9:applicationContext.xml
步骤10:@Component
步骤11:运行测试
步骤 1 : 先运行,看到效果,再学习
老规矩,先下载下载区(点击进入)的可运行项目,配置运行起来,确认可用之后,再学习做了哪些步骤以达到这样的效果。
步骤 2 : 模仿和排错
在确保可运行项目能够正确无误地运行之后,再严格照着教程的步骤,对代码模仿一遍。
模仿过程难免代码有出入,导致无法得到期望的运行结果,此时此刻通过比较正确答案 ( 可运行项目 ) 和自己的代码,来定位问题所在。
采用这种方式,学习有效果,排错有效率,可以较为明显地提升学习速度,跨过学习路上的各个槛。
推荐使用diffmerge软件,进行文件夹比较。把你自己做的项目文件夹,和我的可运行项目文件夹进行比较。
这个软件很牛逼的,可以知道文件夹里哪两个文件不对,并且很明显地标记出来
这里提供了绿色安装和使用教程:diffmerge 下载和使用教程
步骤 3 : 修改applicationContext.xml
1. 在15行添加
<context:annotation-config/> |
表示告诉Spring要用注解的方式进行配置
2. 注入对象的21行注释掉,这个行为在后面将使用注解来完成
<? 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:aop = "http://www.springframework.org/schema/aop" xmlns:tx = "http://www.springframework.org/schema/tx" xmlns:context = "http://www.springframework.org/schema/context" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"> < context:annotation-config /> < bean name = "c" class = "com.how2java.pojo.Category" > < property name = "name" value = "category 1" /> </ bean > < bean name = "p" class = "com.how2java.pojo.Product" > < property name = "name" value = "product1" /> <!-- <property name="category" ref="c" /> --> </ bean > </ beans > |
步骤 4 : @Autowired
在Product.java的category属性前加上@Autowired注解
@Autowired private Category category; |
package com.how2java.pojo; import org.springframework.beans.factory.annotation.Autowired; public class Product { private int id; private String name; @Autowired private Category category; public int getId() { return id; } public void setId( int id) { this .id = id; } public String getName() { return name; } public void setName(String name) { this .name = name; } public Category getCategory() { return category; } public void setCategory(Category category) { this .category = category; } } |
步骤 5 : 运行测试
package com.how2java.test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import com.how2java.pojo.Product; public class TestSpring { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext( new String[] { "applicationContext.xml" }); Product p = (Product) context.getBean( "p" ); System.out.println(p.getName()); System.out.println(p.getCategory().getName()); } } |
步骤 6 : @Autowired的位置
除了前面的 在属性前加上@Autowired 这种方式外,也可以在setCategory方法前加上@Autowired,这样来达到相同的效果
@Autowired public void setCategory(Category category) |
package com.how2java.pojo; import org.springframework.beans.factory.annotation.Autowired; public class Product { private int id; private String name; private Category category; public int getId() { return id; } public void setId( int id) { this .id = id; } public String getName() { return name; } public void setName(String name) { this .name = name; } public Category getCategory() { return category; } @Autowired public void setCategory(Category category) { this .category = category; } } |
步骤 7 : @Resource
除了@Autowired之外,@Resource也是常用的手段
@Resource (name= "c" ) private Category category; |
package com.how2java.pojo; import javax.annotation.Resource; public class Product { private int id; private String name; @Resource (name= "c" ) private Category category; public int getId() { return id; } public void setId( int id) { this .id = id; } public String getName() { return name; } public void setName(String name) { this .name = name; } public Category getCategory() { return category; } public void setCategory(Category category) { this .category = category; } } |
步骤 8 : 对Bean的注解
上述例子是对注入对象行为的注解,那么bean对象本身,比如Category,Product可不可以移出applicationContext.xml配置文件,也通过注解进行呢?
接下来就讲解如何对Bean进行注解配置
步骤 9 : applicationContext.xml
修改applicationContext.xml,什么都去掉,只新增:
<context:component-scan base- package = "com.how2java.pojo" /> |
其作用是告诉Spring,bean都放在com.how2java.pojo这个包下
<?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:aop= "http://www.springframework.org/schema/aop" xmlns:tx= "http://www.springframework.org/schema/tx" xmlns:context= "http://www.springframework.org/schema/context" xsi:schemaLocation=" http: //www.springframework.org/schema/beans http: //www.springframework.org/schema/beans/spring-beans-3.0.xsd http: //www.springframework.org/schema/aop http: //www.springframework.org/schema/aop/spring-aop-3.0.xsd http: //www.springframework.org/schema/tx http: //www.springframework.org/schema/tx/spring-tx-3.0.xsd http: //www.springframework.org/schema/context http: //www.springframework.org/schema/context/spring-context-3.0.xsd"> <context:component-scan base- package = "com.how2java.pojo" /> </beans> |
步骤 10 : @Component
为Product类加上@Component注解,即表明此类是bean
@Component ( "p" ) public class Product { |
为Category 类加上@Component注解,即表明此类是bean
@Component ( "c" ) public class Category { |
另外,因为配置从applicationContext.xml中移出来了,所以属性初始化放在属性声明上进行了。
private String name= "product 1" ; private String name= "category 1" ; |
package com.how2java.pojo; import javax.annotation.Resource; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Component; @Component ( "p" ) public class Product { private int id; private String name= "product 1" ; @Autowired private Category category; public int getId() { return id; } public void setId( int id) { this .id = id; } public String getName() { return name; } public void setName(String name) { this .name = name; } public Category getCategory() { return category; } public void setCategory(Category category) { this .category = category; } } |
package com.how2java.pojo; import org.springframework.stereotype.Component; @Component ( "c" ) public class Category { public int getId() { return id; } public void setId( int id) { this .id = id; } public String getName() { return name; } public void setName(String name) { this .name = name; } private int id; private String name= "category 1" ; } |
步骤 11 : 运行测试
运行TestSpring,可以发现运行结果是一样的
package com.how2java.test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import com.how2java.pojo.Product; public class TestSpring { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext( new String[] { "applicationContext.xml" }); Product p = (Product) context.getBean( "p" ); System.out.println(p.getName()); System.out.println(p.getCategory().getName()); } } |
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