Bspring boot @Autowired使用方式：

1.通過構造器注入
單個

public class TestController (){
private final TestMapper testMapper;
@Autowired
public TestController (TestMapper testMapper) {
this.testMapper= testMapper;
}
}
多個

public class TestController (){
private final TestaMapper testaMapper;
private final TestbMapper testbMapper;
@Autowired
public TestController (TestaMapper testaMapper, TestbMapper testbMapper) {
this.testaMapper= testaMapper;
this.testbMapper= testbMapper;
}
}

弊端：可以看出當需要注入更多的物件時，建構函式的引數值會變得很長。

2.通過setter方法注入

public class TestController (){
private final TestMapper testMapper;
@Autowired
public void setTestMapper(TestMapper testMapper) {
this.testMapper= testMapper;
}
}

弊端：不能將屬性設定為final,每個物件的注入都要寫對應的setter方法。

3.通過field反射注入

public class TestController (){
@Autowired
private TestMapper testMapper;
｝

弊端：方法最簡單。不符合JavaBean規範；不能將屬性設定為final；建立的物件時，還可能引起NullPointerException。

使用idea時會提示Field injection is not recommended

作者：十月是妳的謊言
來源：CSDN
原文：https://blog.csdn.net/qq_38904700/article/details/79515049
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