Spring依赖注入
依赖注入的概念
它是Spring框架核心IOC的具体实现方式。简单的说,就是坐等框架把对象传入,而不用我们自己去获取。
1)构造函数注入(constructor-arg标签)
通过配置的方式,给构造函数的成员变量赋值。
代码:
public class CustomerServiceImpl implements ICustomerService{
private String name;
private Integer age;
private Date birthday;
public CustomerServiceImpl(String name, Integer age, Date birthday) {
this.name = name;
this.age = age;
this.birthday = birthday;
}
@Override
public void saveCustomer() {
}
}
配置如下:
<bean id="customerService" class="com.service.impl.CustomServiceImpl">
<constructor-arg name="name" value="张三"></constructor-arg>
<constructor-arg name="age" value="18"></constructor-arg>
<constructor-arg name="birthday" value="now"></constructor-arg>
</bean>
<bean id="now" class="java.util.Date"></bean>
配置解析:
index:指定参数在构造函数参数列表的索引位置
type: 指定参数在构造函数中的数据类型
name: 指定参数在构造函数的名称
value:它能赋的值是其它的bean类型,也就是说,必须得是在配置文件中配置过的bean
2)set方法注入(property标签)
代码:
public class CustomerServiceImpl implements ICustomerService{
private String name;
private Integer age;
private Date birthday;
public void setName(String name) {
this.name = name;
}
public void setAge(Integer age) {
this.age = age;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
@Override
public void saveCustomer() {
}
}
配置如下:
<bean id="customerService" class="com.service.impl.CustomServiceImpl">
<property name="name" value="张三"></constructor-arg>
<property name="age" value="18"></property>
<property name="birthday" value="now"></property>
</bean>
<bean id="now" class="java.util.Date"></bean>
配置解析:
name: 找的是类中set方法后面的部分
value:给属性赋值是基本数据类型和String类型的
ref:给属性复制是其它的bean类型
3)使用p名称空间注入数据(p标签)
这种方式是通过在xml中导入p空间名称,使用p:propertyName 来注入数据,它的本质仍然是调用类中的set方法实现注入功能。
代码:
public class CustomerServiceImpl implements ICustomerService{
private String name;
private Integer age;
private Date birthday;
public void setName(String name) {
this.name = name;
}
public void setAge(Integer age) {
this.age = age;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
@Override
public void saveCustomer() {
}
}
配置如下:
4)注入集合属性
代码:
package cn.itcast.domain;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Properties;
public class CollBean
{
public CollBean()
{
System.out.println(11111);
}
private String[] ss;
private List ll;
private Map mm;
private Properties properties; //键值对
public void setSs(String[] ss) {
this.ss = ss;
}
public void setLl(List ll) {
this.ll = ll;
}
public void setMm(Map mm) {
this.mm = mm;
}
public void setProperties(Properties properties) {
this.properties = properties;
}
@Override
public String toString() {
return "CollBean [ss=" + Arrays.toString(ss) + ", ll=" + ll + ", mm=" + mm + ", properties=" + properties + "]";
}
}
配置文件:
<bean id="collBean" class="cn.itcast.domain.CollBean">
<property name="ss">
<!-- 数组类型 -->
<list>
<value>aaa</value>
<value>bbb</value>
<value>ccc</value>
</list>
</property>
<property name="ll">
<!-- list类型 -->
<list>
<value>111</value>
<value>222</value>
<ref bean="car"/>
</list>
</property>
<property name="mm">
<!-- map -->
<map>
<entry key="k1" value="aaa"></entry>
<entry key="k2" value="bbbb"></entry>
<entry key="k3" value-ref="car"></entry>
</map>
</property>
<property name="properties">
<!-- properties类型 -->
<props>
<prop key="hibernate.username">root</prop>
<prop key="hibernate.password">1234</prop>
</props>
</property>
</bean>