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This article introduces you how to understand the introduction and configuration of Spring Boot, the content is very detailed, interested friends can refer to, hope to be helpful to you.

1 Spring Boot introduction and configuration 1.1 Spring Boot

Spring Cloud is based on Spring Boot, this section will give a general explanation of Spring Boot, readers can know the role of Spring Boot.

1.1.1 introduction to Spring Boot

To develop a brand-new project, you need to build the development environment first, for example, to determine the technical framework and version, but also to consider the version compatibility between the various frameworks. After completing these tedious work, you have to configure the new project and test whether it can run properly. Finally, the built environment is submitted to other members of the project team for use. It often happens that, on the surface, it has been successfully run, but some project team members are still unable to run, and a lot of time is wasted at the beginning of the project to do this work, and almost every project will put part of the workload into doing these fixed things.

Under the influence of Ruby On Rails, Node.js and other technologies, the field of JavaEE needs a more convenient development way to replace these tedious project construction work. In this context, Spring launched the Spring Boot project, which allows users to build the project more quickly, and users can focus on and quickly devote themselves to the development of business systems. Spring Boot has already prepared the system configuration, the basic code, the jar package that the project depends on, and even the application server used in development. As long as you use the build tool to add the corresponding Spring Boot dependency package when setting up the project, the project can be run, and users do not need to care about version compatibility and other issues.

Spring Boot supports two build tools, Maven and Gradle. Gradle uses Groovy language to write build scripts and has good compatibility with builders such as Maven and Ant. In view of the fact that the author uses Maven more, this book uses Maven as a project building tool. At the time of writing, the latest official version of Spring Boot was 1.5.4, requiring Maven version 3.2 or above.

1.1.2 create a new Maven project

Select "Maven Project" from the New menu and fill in the project information shown in figure 2-5.

Figure 2-5 create a new Maven project

To test the usability of the project, add the web startup module of Spring Boot to make the project function as a Web container, and the contents of the pom.xml file are shown in listing 2-1.

Listing 2-1:codes\ 02\ env-test\ pom.xml

4.0.0 org.crazyit.cloud env-test 0.0.1-SNAPSHOT org.springframework.boot spring-boot-starter-web 1.5.4.RELEASE

After configuring the dependency, the dependency will automatically help our project to add other Spring modules and dependent third-party packages, such as spring-core, sprin-beans, spring-mvc, etc., in addition to these modules, but also added embedded Tomcat.

1.1.3 write startup classes

Once the dependency is added, you only need to write a simple startup class to start the Web service, as shown in listing 2-2.

Listing 2-2:codes\ 02\ env-test\ src\ main\ java\ org\ crazyit\ cloud\ MyApplication.java

Package org.crazyit.cloud;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class MyApplication {public static void main (String [] args) {SpringApplication.run (MyApplication.class, args);}}

The MyApplication class uses the @ SpringBootApplication annotation, which declares that the class is a SpringBoot application with the functions of "@ SpringBootConfiguration, @ EnableAutoConfiguration, @ ComponentScan" and so on. Run the main method of MyApplication directly, and when you see the following output message, it proves that the startup is successful:

2017-08-02 20 o.s.w.s.handler.SimpleUrlHandlerMapping 53 INFO 05.327 INFO 1976-[main] o.s.w.s.handler.SimpleUrlHandlerMapping: Mapped URL path [/ * * / favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler] 2017-08-02 20 o.s.w.s.handler.SimpleUrlHandlerMapping 53 o.s.w.s.handler.SimpleUrlHandlerMapping 05.530 INFO 1976-[main] o.s.j.e.a.AnnotationMBeanExporter: Registering beans for JMX exposure on startup2017-08 -02 20 Tomcat started on port 53 INFO 1976-[main] s.b.c.e.t.TomcatEmbeddedServletContainer: Tomcat started on port (s): 8080 (http) 2017-08-02 20 53 INFO 05.885 INFO 1976-[main] org.crazyit.cloud.MyApplication: Started MyApplication in 5.758 seconds (JVM running for 6.426)

According to the output information, the Tomcat port launched is 8080. Open the browser to visit: http://localhost:8080, you can see the error page, indicating that the application has been started successfully.

1.1.4 write a controller

The spring-boot-starter-web module added in the previous section integrates SpringMVC by default, so you only need to write a Controller to implement the simplest HelloWord program. Listing 2-3 is the controller.

Listing 2-3:codes\ 02\ env-test\ src\ main\ java\ org\ crazyit\ cloud\ MyController.java

Package org.crazyit.cloud;import org.springframework.http.MediaType;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;import org.springframework.web.bind.annotation.ResponseBody;import org.springframework.web.bind.annotation.RestController @ Controllerpublic class MyController {@ GetMapping ("/ hello") @ ResponseBody public String hello () {return "Hello World";}}

The @ Controller annotation is used to decorate the MyController in listing 2-3. Because the @ SpringBootApplication annotation is used in the startup class, which contains the function of @ ComponentScan, @ Controller is scanned and registered. The @ GetMapping and @ ResponseBody annotations are used in the hello method to declare the access address of the hello method and what is returned. Rerun the startup class, open the browser and visit the following address: http://localhost:8080/hello, and you can see the return of the controller.

1.1.5 release REST WebService

Spring MVC supports the direct release of REST-style WebService and the creation of a new test object Person, as shown in listing 2-4.

Listing 2-4:codes\ 02\ env-test\ src\ main\ java\ org\ crazyit\ cloud\ Person.java

Package org.crazyit.cloud;public class Person {private Integer id; private String name; private Integer age; public Integer getId () {return id;} public void setId (Integer id) {this.id = id;} public String getName () {return name } public void setName (String name) {this.name = name;} public Integer getAge () {return age;} public void setAge (Integer age) {this.age = age;}}

Modify the controller class, as shown in listing 2-5.

Listing 2-5:codes\ 02\ env-test\ src\ main\ java\ org\ crazyit\ cloud\ MyController.java

Package org.crazyit.cloud;import org.springframework.http.MediaType;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;import org.springframework.web.bind.annotation.ResponseBody;import org.springframework.web.bind.annotation.RestController @ RestControllerpublic class MyController {@ GetMapping ("/ hello") public String hello () {return "Hello World";} @ RequestMapping (value = "/ person/ {personId}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE) public Person findPerson (@ PathVariable ("personId") Integer personId) {Person p = new Person (); p.setId (personId) P.setName ("Crazyit"); p.setAge (30); return p;}}

In the MyController class, change the original @ Controller annotation to @ RestController, and the original hello method no longer needs to be decorated with @ ResponseBody. @ RestController already contains the @ ResponseBody annotation. Create a new findPerson method, which will create an instance of Person based on the parameter id and return. Accessing this method will result in a JSON string. Run the startup class, enter: http://localhost:8080/person/1 in the browser, and you can see that the interface returns the following JSON string:

{"id": 1, "name": "Crazyit", "age": 30}

There are many ways to invoke REST services, which will be covered in later chapters.

1.2 Spring Boot profile

Spring Cloud is built on Spring Boot, and the configuration of many modules is placed in the configuration file of Spring Boot, so it is necessary to understand the configuration file rules of Spring Boot to lay the foundation for the following chapters.

1.2.1 default profile

Spring Boot reads various configurations sequentially, such as command line parameters, system parameters, and so on. This chapter only deals with parameter reading for configuration files. By default, Spring Boot reads application.properties or application.yml files in the following directory in order:

The config directory of the root directory of the  project.

 project root directory.

The config directory under the  project classpath.

 project classpath root directory.

If you have any questions about the above description, please refer to figure 2-6.

Figure 2-6 configuration file reading order

The numbers in figure 2-6 are the order in which the files are read. The boot-config-file project used in this section relies on the spring-boot-starter-web project to add the following dependencies to pom.xml:

Org.springframework.boot spring-boot-starter-web 1.5.4.RELEASE 1.2.2 specify the profile location

If you want to specify the configuration file yourself, you can add parameters to the startup command of the Spring container, as shown in listing 2-6.

Listing 2-6:codes\ 02\ boot-config-file\ src\ main\ java\ org\ crazyit\ boot\ TestDefaultFile.java

Package org.crazyit.boot;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.builder.SpringApplicationBuilder;import org.springframework.context.ConfigurableApplicationContext @ SpringBootApplicationpublic class TestDefaultFile {public static void main (String [] args) {ConfigurableApplicationContext context = new SpringApplicationBuilder (TestDefaultFile.class) .propertie s ("spring.config.location=classpath:/test-folder/my-config.properties") .run (args) / / output variable System.out.println (context.getEnvironment () .getProperty ("jdbc.user"));}

The TestDefaultFile class, when using SpringApplicationBuilder, configures the spring.config.location property to set the configuration file to be read.

1.2.3 yml Fil

YAML language uses a convenient format for data configuration, through configuration layering, indentation, greatly enhance the readability of the configuration file, using the Yaml language configuration file with the suffix ".yml". Listing 2-7 is a yml configuration file.

Listing 2-7:codes\ 02\ boot-config-file\ src\ main\ resources\ my-config.yml

Jdbc: user: root passwd: 123456 driver: com.mysql.jdbc.Driver

Here, it is important to note that each line is configured to be indented by spaces, not by the tab key. The properties file corresponding to listing 2-7 is as follows:

The jdbc.user=rootjdbc.passwd=123456jdbc.driver=com.mysql.jdbc.Driver1.2.4 runtime specifies the profiles configuration

If you activate different configurations in different environments, you can use profiles, with two profiles configured in listing 2-8.

Listing 2-8:codes\ 02\ boot-config-file\ src\ main\ resources\ test-profiles.yml

Spring: profiles: mysqljdbc: driver: com.mysql.jdbc.Driver---spring: profiles: oraclejdbc: driver: oracle.jdbc.driver.OracleDriver

It is defined that the two profiles,profiels of mysql and oracle are separated by "- -", and when the Spring container starts, use spring.profiles.active to specify which profiles to activate, as shown in listing 2-9.

Listing 2-9:codes\ 02\ boot-config-file\ src\ main\ java\ org\ crazyit\ boot\ TestProfiles.java

Package org.crazyit.boot;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.builder.SpringApplicationBuilder;import org.springframework.context.ConfigurableApplicationContext @ SpringBootApplicationpublic class TestProfiles {public static void main (String [] args) {ConfigurableApplicationContext context = new SpringApplicationBuilder (TestProfiles.class) .properties ("spring.config.location=classpath:/test-profiles.yml") .properties ("spring.profiles.active=oracle") .run (args) / / output variable System.out.println (context.getEnvironment () .getProperty ("jdbc.driver")) / / start the second Spring container The specified port is 8081 ConfigurableApplicationContext context2 = new SpringApplicationBuilder (TestProfiles.class) .properties ("spring.config.location=classpath:/test-profiles.yml") .properties ("spring.profiles") .active = mysql ") .properties (" server.port=8081 ") .run (args) / / output variable System.out.println (context2.getEnvironment () .getProperty ("jdbc.driver"));}}

After you have some understanding of the configuration file of Spring Boot, you will be familiar with the configuration content of Spring Cloud in the following chapter.

1.2.5 Hot deployment

Each time you modify Java, you need to rerun the Main method to take effect. This will reduce the development effect. We can use the development tools provided by Spring Boot to achieve hot deployment and add the following dependencies to the project:

Org.springframework.boot spring-boot-devtools

When the Java file is modified, the container reloads the Java class of the project.

The editor mainly talks about the construction of the basic environment of this book, readers mainly master the use of Maven, and almost all the cases in this book are Maven projects. The Spring Cloud project is built on the basis of Spring Boot, and most of the cases are also based on Spring Boot. This chapter gives a general explanation of Spring Boot and demonstrates the convenience of Spring Boot with an example of Hello World. After studying this chapter, readers will know the general functions of Spring Boot and can achieve the goal.

On how to understand the introduction and configuration of Spring Boot to share here, I hope that the above content can be of some help to you, can learn more knowledge. If you think the article is good, you can share it for more people to see.

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