One 、 Object data source management

Object data source management ： in other words , Manage... Provided by third parties bean object

1.1、 Let's manage druid The example of Druid object resource is shown as follows ：

First step ： Import druid coordinate ：

  The second step ：IOC Manage third parties in containers bean：

Be careful 1： When checking which method to inject , Enter the first bean In the object , Then press ctrl+F12 Check whether to use constructor or setter Injection mode

Be careful 2： Here is why we use value instead of ref： Because in DriudDataSource Among the objects , Ahead name The attribute value in this object is represented by the attribute , Such as ：private String name Format exists , Not in BookDao bookdao = new BookDaoImpl(); Format exists , So want to use value Rather than using ref 【 That's what I learned earlier setter Injection handles simple types 】

The third step ： obtain IOC Managed in a container bean Object calls methods in the object （ Here we are not connected to our database , Only print the memory address of the object ）

  The running results are as follows ：

1.2、 Let's manage C3P0 An example of an object resource is shown below ：

Be careful ：C3P0 It is also used to connect to the database , and druid The difference is that the coordinates also need to be imported mysql drive jar Coordinates of the package

First step ： Import C3P0 Coordinates and mysql drive jar Package coordinates

  The second step ：IOC Manage third parties in containers bean：

The third step ： obtain IOC Managed in a container bean Object calls methods in the object （ Here we are not connected to our database , Only print the memory address of the object ）

  The running results are as follows ：

Two 、 load properties file

load properties file ： Just put the bean The dependencies made in the object value value , Write to properties The file of , And then get value value

2.1、 load properties The file steps are as follows

 jdbc.properties file ：

 spring.xml file ：

 test：

 2.2、 Verify whether you can get properties The data in the file

properties file ：

 BookDaoImpl：

  The running results are as follows ：

 2.3、 A small problem （ stay properties The attribute name in the file conflicts with the attribute name of the environment variable ）

： occasionally properties Attribute name in the file （ Such as ：username） Will be compared with username Property name conflict , also properties The priority of the file is lower than that of the environment variable , So sometimes what you get is not properties Attribute values in the file , It's the environment variable

  The running results are as follows ：

The solution to this small problem is as follows ：

  The operation results are as follows ：（ You will find that there is no conflict , Because the resources in the environment variable are no longer loaded ）

2.4、 Load multiple properties file