Spring注入参数

[zhaozhao15]

Spring注入参数

---

1. 注入基本类型值
2. 注入bean
3. 内部bean
4. null值
5. 级联属性
6. 集合类型属性

package com.java1234.entity;

public class Dog {
	private String name;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
}

package com.java1234.entity;

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 People {
	private int id;
	private String name;
	private int age;
	private Dog dog;
	private List<String> hobbies=new ArrayList<String>();
	private Set<String> loves=new HashSet<String>();
	private Map<String,String> works=new HashMap<String,String>();
	private Properties addresses=new Properties();
	
	public People() {
		super();
	}
	public People(int id, String name, int age) {
		super();
		this.id = id;
		this.name = name;
		this.age = age;
	}

	public Set<String> getLoves() {
		return loves;
	}
	public void setLoves(Set<String> loves) {
		this.loves = loves;
	}
	public List<String> getHobbies() {
		return hobbies;
	}
	public void setHobbies(List<String> hobbies) {
		this.hobbies = hobbies;
	}
	public Map<String, String> getWorks() {
		return works;
	}
	public void setWorks(Map<String, String> works) {
		this.works = works;
	}
	public Properties getAddresses() {
		return addresses;
	}
	public void setAddresses(Properties addresses) {
		this.addresses = addresses;
	}
	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;
	}

	@Override
	public String toString() {
		return "People [id=" + id + ", name=" + name + ", age=" + age
				+ ", dog=" + dog + ", hobbies=" + hobbies + ", loves=" + loves
				+ ", works=" + works + ", addresses=" + addresses + "]";
	}
}

来看bean

1. 注入基本类型值

最简单的，注入基本类型。

    <bean id="people1" class="com.java1234.entity.People">
		<property name="id" value="1"></property>
		<property name="name" value="张三"></property>
		<property name="age" value="11"></property>
	</bean>

2. 注入bean

我们给people2注入的不是普通的属性，是一个bean——dog1。
ref="dog1"表示引用的是一个bean，不再是value。
这是spring管理的bean之间的嵌套。

    <bean id="dog1" class="com.java1234.entity.Dog">
		<property name="name" value="Jack"></property>
	</bean>
	
	<bean id="people2" class="com.java1234.entity.People">
		<property name="id" value="1"></property>
		<property name="name" value="张三"></property>
		<property name="age" value="11"></property>
		<property name="dog" ref="dog1"></property>
	</bean>

3. 内部bean注入

现在这个dog1即可以被people1引用也可以被people2引用，我们现在要一个新的狗，只能被一个people引用。
我们直接在bean内部注入属性。这个“内部”顾名思义，很好理解。

    <bean id="people3" class="com.java1234.entity.People">
		<property name="id" value="1"></property>
		<property name="name" value="张三"></property>
		<property name="age" value="11"></property>
		<property name="dog">
			<bean class="com.java1234.entity.Dog">
				<property name="name" value="Tom"></property>
			</bean>
		</property>
	</bean>

4. null值

假如说一个人没有狗。
属性dog内部直接是null。
（注意空指针异常）

    <bean id="people4" class="com.java1234.entity.People">
		<property name="id" value="1"></property>
		<property name="name" value="张三"></property>
		<property name="age" value="11"></property>
		<property name="dog">
			<null></null>
		</property>
	</bean>

5. 级联属性

dog.name是直接级联到了dog对象的name属性，而不像我们之前需要注入一个dog的bean。
需要注意我们在people类中必须要自己new一个dog实例，不然没有dog，显然直接去设置dog.name会有空指针异常，因为实际上相当于需要调用dog的set方法。

    <bean id="people5" class="com.java1234.entity.People">
		<property name="id" value="1"></property>
		<property name="name" value="张三"></property>
		<property name="age" value="11"></property>
		<property name="dog.name" value="Jack2"></property>
	</bean>

6. 集合类型属性

我们注入的属性是集合类型，比如list、set、map、properties。
在配置文件中看起来还是比较清晰的。

    <bean id="people6" class="com.java1234.entity.People">
		<property name="id" value="1"></property>
		<property name="name" value="蔡徐坤"></property>
		<property name="age" value="11"></property>
		<property name="dog" ref="dog1"></property>
		<property name="hobbies">
			<list>
				<value>唱歌</value>
				<value>跳舞</value>
			</list>
		</property>
		<property name="loves">
			<set>
				<value>Rap</value>
				<value>打篮球</value>
			</set>
		</property>
		<property name="works">
			<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>
		<property name="addresses">
			<props>
				<prop key="address1">aaaaa</prop>
				<prop key="address2">bbbbb</prop>
			</props>
		</property>
	</bean>

---

最后是测试代码，OK。

public class T {
	private ApplicationContext ac;

	@Before
	public void setUp() throws Exception {
		ac=new ClassPathXmlApplicationContext("beans.xml");
	}

	// 基本类型值
	@Test
	public void test1() {
		People people=(People)ac.getBean("people1");
		System.out.println(people);
	}
	
	// 注入bean
	@Test
	public void test2() {
		People people=(People)ac.getBean("people2");
		System.out.println(people);
	}
	
	// 内部bean
	@Test
	public void test3() {
		People people=(People)ac.getBean("people3");
		System.out.println(people);
	}
	
	// 注入null
	@Test
	public void test4() {
		People people=(People)ac.getBean("people4");
		System.out.println(people);
	}
	
	// 级联属性
	@Test
	public void test5() {
		People people=(People)ac.getBean("people5");
		System.out.println(people);
	}
	
	// 注入集合
	@Test
	public void test6() {
		People people=(People)ac.getBean("people6");
		System.out.println(people);
	}
}