Spring 依赖注入(注入参数)
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注入参数基本分7类：
1.基本类型值
2.注入bean
3.内部bean
4.注入null值
5.级联属性
6.List，Set，Map集合的注入
7.properties文件的注入（和集合注入基本是一样的）
下面就是实体类People2，beans.xml的源码
package com.maya.model;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
public class People2 {
private int id;
private String name;
private int age;
private Dog dog;//注入bean
private List<String> myList=new ArrayList<String>();//List集合注入
private Set<String> mySet=new HashSet<String>();//Set集合注入
private Map<String,String> myMap=new HashMap<String,String>();//Map集合注入
private Properties jdbc=new Properties();//properties文件注入，和map差不多都是以key、value的形式
public Map<String, String> getMyMap() {
return myMap;
}
public void setMyMap(Map<String, String> myMap) {
this.myMap = myMap;
}
public Set<String> getMySet() {
return mySet;
}
public void setMySet(Set<String> mySet) {
this.mySet = mySet;
}
public List<String> getMyList() {
return myList;
}
public void setMyList(List<String> myList) {
this.myList = myList;
}
public Dog getDog() {
return dog;
}
public void setDog(Dog dog) {
this.dog = dog;
}
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public People2() {
super();
}
public People2(int id, String name, int age, Dog dog) {
super();
this.id = id;
this.name = name;
this.age = age;
this.dog = dog;
}
public Properties getJdbc() {
return jdbc;
}
public void setJdbc(Properties jdbc) {
this.jdbc = jdbc;
}
@Override
public String toString() {
return "People2 [id=" + id + ", name=" + name + ", age=" + age + ", dog=" + dog + ", myList=" + myList
+ ", mySet=" + mySet + ", myMap=" + myMap + ", jdbc=" + jdbc + "]";
}
//当要使用dog.name是就要注意beans.xml文件的配置
}
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<!-- 注入参数 -->
<!-- 基本类型注入 -->
<bean id="people21" class="com.maya.model.People2">
<constructor-arg name="id" value="0"></constructor-arg>
<constructor-arg name="name" value="张三"></constructor-arg>
<constructor-arg name="age" value="10"></constructor-arg>
<constructor-arg name="dog" ref="dog1"></constructor-arg>
</bean>
<!-- 注入bean -->
<bean id="dog1" class="com.maya.model.Dog">
<property name="name" value="阿黄"></property>
</bean>
<bean id="people22" class="com.maya.model.People2">
<property name="id" value="1"></property>
<property name="name" value="小明2"></property>
<property name="age" value="22"></property>
<property name="dog" ref="dog1"></property><!-- 注入bean时ref是要注入的bean的id -->
</bean>
<!-- 注入内部bean -->
<bean id="people23" class="com.maya.model.People2">
<property name="id" value="3"></property>
<property name="name" value="小明3"></property>
<property name="age" value="33"></property>
<property name="dog">
<bean class="com.maya.model.Dog">
<property name="name" value="UZI"></property><!-- 分开写而已 -->
</bean>
</property>
</bean>
<!-- 注入null -->
<bean id="people24" class="com.maya.model.People2">
<property name="id" value="3"></property>
<property name="name" value="小明3"></property>
<property name="age" value="33"></property>
<property name="dog">
<null></null><!-- 给dog属性注入一个null -->
</property>
</bean>
<!-- 级联方式注入 -->
<!-- <bean id="people25" class="com.maya.model.People2">
<property name="id" value="3"></property>
<property name="name" value="小明3"></property>
<property name="age" value="33"></property>
<property name="dog.name" value="小明的狗"></property>
注意：以这种方式进行赋值时，因为我们没用注入Dog的实例对象，所以我们要在People2的dog属性后new一个Dog实例！这样才能成功赋值
</bean> -->
<!-- 注入List集合,Set集合,Map集合 -->
<bean id="people26" class="com.maya.model.People2">
<property name="id" value="3"></property>
<property name="name" value="小明3"></property>
<property name="age" value="33"></property>
<property name="dog" ref="dog1"></property>
<!-- List集合 -->
<property name="myList">
<list>
<value>a</value>
<value>b</value>
<value>c</value>
<value>d</value>
</list>
</property>
<!-- Set集合，Set集合是自动去掉重复值得！所以输出的结果还是a,b,c -->
<property name="mySet">
<set>
<value>a</value>
<value>b</value>
<value>c</value>
<value>c</value>
<value>b</value>
<value>a</value>
</set>
</property>
<!-- Map集合 -->
<property name="myMap">
<map>
<entry>
<key><value>上午</value></key>
<value>写代码</value>
</entry>
<entry>
<key><value>下午</value></key>
<value>测试代码</value>
</entry>
</map>
</property>
<!-- 配置properties文件 -->
<property name="jdbc">
<props>
<prop key="qd">com.mysql.jdbc.Driver</prop>
<prop key="url">jdbc:mysql://localhost:3306/spring4?characterEncoding=GBK</prop>
<prop key="user">root</prop>
</props>
</property>
</bean>
<!-- 配置properties文件 -->
<bean id="people27" class="com.maya.model.People2">
<!-- 在这之前没有为其他属性赋值，这是可以得。但是当使用其引用bean的某些方法时就必须给其赋值而且不能是null -->
<property name="jdbc">
<props>
<prop key="qd">com.mysql.jdbc.Driver</prop>
<prop key="url">jdbc:mysql://localhost:3306/spring4?characterEncoding=GBK</prop>
<prop key="user">root</prop>
</props>
</property>
</bean>
</beans>
常见错误：
Could not resolve matching constructor（构造函数问题）
Loading XML bean definitions from class path resource（实体类中 引用的其他bean类正在使用它的某些方法！去掉使用的方法就好了）
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