Spring IOC

Posted 2021-03-11 zhuob

创建Bean

通过属性创建

实体类Category

public class Category {
    private int id;
    private String name;


    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;
    }
}

实体类Product

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;
    }

    public void setCategory(Category category) {
        this.category = category;
    }
}

通过标签

  <bean name="c" class="com.how2java.pojo.Category">
        <property name="id" value="category 1"/>
    </bean>

   <bean name="p2" class="com.how2java.pojo.Product" >
        <property name="id" value="1"></property>
        <property name="name" value="p"></property>
        //引用类型
        <property name="category" ref="c"></property>
    </bean>

通过 p 命名空间 需要在applicationContext中增加命名空间

    <bean name="c" class="com.how2java.pojo.Category" p:name="category 2">

    //引用类型
    <bean name="p" class="com.how2java.pojo.Product" p:name="product1" p:id="1" p:category-ref="c"></bean>

通过自动装配@Autowired

//首先需要在applicationContext.xml中增加
<context:annotation-config/>
   <bean name="p" class="com.how2java.pojo.Product" >
        <property name="id" value="1"></property>
        <property name="name" value="p"></property>
    </bean>
//这里并没有配置Category，但是测试中仍然成功，因为
public class Product {
    private int id;
    private String name;
    @Autowired
    private Category category;

    public int getId() {
        return id;
    }
...}
这里设置为category 自动装配


  @Autowired
    public Category getCategory() {
        return category;
    }
也可以在setter方法上注入

通过Resource 可以指定Bean

  @Resource //不一定是c
    private Category category;

  @Resource(name="c") //指定只能是 c
    private Category category;

context:component-scan

<context:component-scan base-package="com.how2java.pojo"/>//扫描包下的包，不需要xml配置

@Component("p")
public class Product {
    private int id;
    private String name;
    @Resource
    private Category category;

@Component("c")
public class Category {
    private int id;
    private String name;
//但是属性值为空
//设置<context:component-scan之后，能自动找到autowired装配的bean，不需要annotion-config了