常见的依赖注入

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依赖注入主要有两种方式DI，即构造器注入和Setter注入(常用)

1:构造函数注入,注意参数为引用类型和普通类型的配置区别, 用例：

package x.y;public class Foo { private Bar bar = null; private Bar baz = null; private int count; public Foo(Bar bar, Baz baz, int count) { // ... }}//第一种配置<beans> <bean id="bar" class="x.y.Bar"/> <bean id="baz" class="x.y.Baz"/> <bean id="foo" class="x.y.Foo"> <constructor-arg ref="bar"/> <constructor-arg ref="baz"/> <constructor-arg type="int" value="7500"/> </bean></beans>//第二种配置<beans> <bean name="foo" class="x.y.Foo"> <constructor-arg> <bean class="x.y.Bar"/> </constructor-arg> <constructor-arg> <bean class="x.y.Baz"/> </constructor-arg> <constructor-arg type="int" value="7500"/> </bean></beans>

2:setter方法注入,注意提供set方法,用例:

package x.y;public class Foo { private Bar bar = null; private Bar baz = null; private int count; public Foo() { // ... } public void setBar(Bar bar) { this.bar = bar; } public void setBar(Bar baz) { this.baz = baz; } public void setCount(int count) { this.count = count; }}<beans> <bean id="bar" class="x.y.Bar"/> <bean id="baz" class="x.y.Baz"/> <bean id="foo" class="x.y.Foo"> <property name="bar" ref="bar"/> <property name="baz" ref="baz"/> <property name="count" value="7500"/> </bean></beans>

3.常见的一些注入: int, String, List, Set, Array, Map

<bean id="bean1" class="com.beans.Bean1"><property name="strValue"><value>strValue</value></property><property name="intValue"><value>12345</value></property><property name="listValue"><list><value>list1</value><value>list2</value></list></property><property name="setValue"><set><value>set1</value><value>set2</value></set></property><property name="arrayValue"><list><value>arrayValue1</value><value>arrayValue1</value></list></property><property name="mapValue"><map><entry key="k1" value="k1"></entry><entry> <key> <value>k2</value> </key> <value>k2</value> </entry></map></property></bean>

4: 将公共的注入定义描述出来

* 通过<bean>标签定义公共的属性，指定abstract=true
* 具有相同属性的类在<bean>标签中指定其parent属性

public class Bean2 {private String id;private String name;private String pw; //..set}public class Bean3 {private String id;private String name; //..set}将这两个类中公共的部分提取出来，减少配置！