春天的订单依赖注入是什么？ [英] Whats is the order dependency injection in spring?

问题描述

我对弹簧依赖注入有疑问。
我需要知道依赖项是按照XML中声明的顺序注入的，还是
没有这样的顺序。

I have a question regarding spring dependency injection. I need to know whether dependency gets injected in the order in which it has been declared in the XML or there is no order as such.

示例：

<bean id="empBean" class="com.test.EmployeeBean">
      <property name="jdbcTemplate" ref="jdbcTemplate" />
       <property name="empAddress" ref="empAddress" />
    </bean>

我们可以保证总是 jdbcTemplate 在 empName 之前初始化？请帮助

Can we guarantee that always jdbcTemplate will be initialized before empName? Please help

推荐答案

您不能保证将它们以任何特定顺序注入，因此您应该设计Bean，使其不会没关系-这很容易实现。

You cannot guarantee that these will be injected in any particular order, and you should design your beans such that it doesn't matter -- which is easy to achieve.

所以此类是不好的代码，因为在bean创建之后，其状态将根据Spring注入的顺序而有所不同。 ：

So this class is bad code, because its state after bean-creation will differ depending on the order Spring happens to inject:

public class BadClass {
    private String foo = "";
    private String foobar = "";

    public void setFoo(String foo) {
        this.foo = foo;
    }

    public void setBar(String bar) {
        this.foobar = foo + bar;
    }

    public String toString() {
        return foobar;
    }
}

原因：

 BadClass c = new BadClass(); 
 c.setFoo("foo");
 c.setBar("bar"); 
 return c.toString()` 

... return $ foobar 。

... returns "foobar".

 BadClass c = new BadClass(); 
 c.setBar("bar"); 
 c.setFoo("foo");
 return c.toString()` 

... return bar 。

... returns "bar".

许多人认为使用构造函数注入是最佳实践，在这种情况下，所有注入都将在一次调用中

Many people think it's best practice to use constructor injection, in which case all the injections will occur in one invocation of the constructor.

public class BetterClass {
    private String foo = "";
    private String foobar = "";

    public BetterClass(String foo, String bar) {
        this.foo = foo;
        this.foobar = foo + bar;
    }

    public String toString() {
        return foobar;
    }
}

这篇关于春天的订单依赖注入是什么？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！