Spring根据XML配置文件注入属性

方法一使用setter方法

package com.swift;

public class Book {
    private String bookName;

    public void setBook(String bookName) {
        this.bookName = bookName;
    }

    @Override
    public String toString() {
        return "Book [book=" + bookName + "]";
    }
}

在Spring框架中，假定Servlet类中不能直接生成Book类的对象，并注入String bookName的属性值

而需要通过配置文件xml的方法

<?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">
<!-- IoC 控制反转 SpringSpring根据XML配置文件注入属性 -->
<bean id="book" class="com.swift.Book">
<property name="bookName" value="三体——黑暗森林"></property>
</bean>
</beans>

Servlet类代码：

package com.swift;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

@WebServlet("/book")
public class BookServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    public BookServlet() {
        super();
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().append("Served at: ").append(request.getContextPath());
        @SuppressWarnings("resource")
        //就是下边这几句了
        ApplicationContext context=new ClassPathXmlApplicationContext("a.xml");
        Book book=(Book) context.getBean("book");
        String bookInfo=book.fun();
        response.getWriter().println();
        response.getWriter().append(bookInfo);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

注意

beans 、context、core 和expression核心jar包

以及commons-logging 和log4j两个jar包不要缺少

方法二使用有参构造方法