XML 通过静态工厂方法注入 Bean
1. 创建一个 User 类和对应的工厂类 UserFactory
User.java
public class User {
private String name;
private int age;
public User() {
System.out.println("调用User类的无参构造方法");
}
public void sayHello(String name){
System.out.println("hello, " + name + "!");
}
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;
}
}
UserFactory.java
public class UserFactory {
public static User getInstance(){
return new User();
}
}
2. 在 Spring 配置文件通过静态工厂方法注入 User 的 Bean
<bean class="org.daistudy.UserFactory" factory-method="getInstance" id="user2"/>
3. 初始化 Spring 的 IoC 容器,并获取 User Bean
User user = (User) context.getBean("user2");
user.sayHello("王五");
4. 适用场景及示例代码
在一些第三方框架适用过程中,无法直接通过普通构造方法注入,则不得不适用静态工厂方式或实例工厂方法注入。例如,在使用 OkHttp 时,由于创建 OkHttpClient 对象时需要先创建一个 Builder 来设置相关属性,此时如果想注入 Bean 则不得不使用静态工厂方法注入。
OkHttpClientFactory.java
public class OkHttpClientFactory {
public static OkHttpClient getInstance(){
OkHttpClient okHttpClient = new OkHttpClient
.Builder()
.connectTimeout(5, TimeUnit.SECONDS)
.readTimeout(5, TimeUnit.SECONDS)
.build();
return okHttpClient;
}
}
静态工厂方法注入 OkHttpClient 的 Bean
<bean class="org.daistudy.OkHttpClientFactory" factory-method="getInstance" id="okHttpClient"/>
应用,下载一个图片
public class DownloadImage {
public static void main(String[] args) {
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
OkHttpClient okHttpClient = (OkHttpClient) context.getBean("okHttpClient");
Request request = new Request.Builder().url("http://pic.netbian.com/uploads/allimg/180826/113958-153525479855be.jpg").get().build();
okHttpClient.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
}
@Override
public void onResponse(Call call, Response response) throws IOException {
// save image
if (response.isSuccessful()) {
InputStream inputStream = response.body().byteStream();
FileOutputStream fileOutputStream = new FileOutputStream(new File("E:\\1.png"));
byte[] buf = new byte[1024];
int len = 0;
while((len = inputStream.read(buf)) != -1){
fileOutputStream.write(buf, 0, len);
fileOutputStream.flush();
}
fileOutputStream.close();
inputStream.close();
}
}
});
}
}
网友评论