Spring 依賴注入的4種方式

一、Set注入

必須要有setter方法

public class UserDao {public void test(){System.out.println("=====test======");} } package com.yao.service;import com.yao.pojo.UserDao;public class UserService {private UserDao userDao;public void setUserDao(UserDao userDao) {this.userDao = userDao;}public void test(){System.out.println("UserService.test");} } <bean id="userDao" class="com.yao.pojo.UserDao"/><bean id="userService" class="com.yao.service.UserService"><property name="userDao" ref="userDao"/></bean>

二、構造器注入

必須要有有參構造方法

package com.yao.service;import com.yao.pojo.UserDao;public class UserService {private UserDao userDao;public UserService(UserDao userDao) {this.userDao = userDao;}public void test(){System.out.println("UserService.test");} } <bean id="userDao" class="com.yao.pojo.UserDao"/><bean id="userService" class="com.yao.service.UserService"><constructor-arg index="0" name="userDao" ref="userDao"/> </bean>

三、靜態工廠方法注入

package com.yao.factory;import com.yao.pojo.UserDao;public class Factory {public static UserDao getUserDao(){return new UserDao();} } <bean id="userDao" class="com.yao.factory.Factory" factory-method="getUserDao"/><bean id="userService" class="com.yao.service.UserService"><property name="userDao" ref="userDao"/></bean>

四、實例工廠方法注入

package com.yao.factory;import com.yao.pojo.UserDao;public class Factory {// 靜態工廠public static UserDao getUserDao(){return new UserDao();}// 實例工廠public UserDao userDao(){return new UserDao();} } <bean id="factory" class="com.yao.factory.Factory"/><bean id="userDao2" factory-bean="factory" factory-method="userDao"/><bean id="userService" class="com.yao.service.UserService"><property name="userDao" ref="userDao2"></property></bean>

總結

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