spring boot debug using maven

初始化本地 git 仓库的脚本

git init --bare spring-boot-debug.git
git clone spring-boot-debug.git
cd spring-boot-debug
mkdir -p src/main/java/com/example/boot/controller
mkdir -p src/main/resources

### create pom.xml and java files ###
touch pom.xml
touch src/main/java/com/example/boot/SpringBootDebugApplication.java
touch src/main/java/com/example/boot/controller/DebugController.java
git add -A :/
git commit -am "init spring boot application"
git push

spring boot 项目的 pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
    </parent>

    <groupId>com.example.spring</groupId>
    <artifactId>spring-boot-debug</artifactId>
    <packaging>jar</packaging>
    <name>${project.artifactId}</name>
    <version>0.0.1-SNAPSHOT</version>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
    </dependencies>

    <build>
        <finalName>${project.artifactId}</finalName>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>${project.parent.version}</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>build-info</goal>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>pl.project13.maven</groupId>
                <artifactId>git-commit-id-plugin</artifactId>
                <version>2.2.4</version>
                <executions>
                    <execution>
                        <id>get-the-git-infos</id>
                        <goals>
                            <goal>revision</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <generateGitPropertiesFile>true</generateGitPropertiesFile>
                    <dotGitDirectory>${project.basedir}/.git</dotGitDirectory>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

spring boot 应用程序 SpringBootDebugApplication

package com.example.boot;

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;

@SpringBootApplication
public class SpringBootDebugApplication {

    public static void main(String[] args) {
        new SpringApplicationBuilder(SpringBootDebugApplication.class).run(args);
    }

}

测试的 DebugController

package com.example.boot.controller;

import javax.servlet.http.HttpServletRequest;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class DebugController {

    private static final Logger LOGGER = LoggerFactory.getLogger(DebugController.class);

    @RequestMapping("index")
    public String index(HttpServletRequest httpServletRequest) {
        String host = httpServletRequest.getRemoteHost();
        int port = httpServletRequest.getRemotePort();
        LOGGER.info("add breakpoint at this line, host is {}, and port is {}", host, port);
        return host;
    }

}

mvnDebug spring-boot:run

如下方式运行项目，虽然这里提示在8000端口监听客户端的连接，并且可以使用jdb连接调试，也可以用vscode连接调试，但使用IDEA开发工具Attach to Local Process...时，并没有发现待调试程序在8000端口上运行。

 mvnDebug spring-boot:run
Preparing to execute Maven in debug mode
Listening for transport dt_socket at address: 8000

jdb attach

jdb是基于命令行的工具，设置好断点，再访问http://localhost:8080/index页面，就会进入断点。

 jdb -attach 8000
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
Initializing jdb ...
>
VM Started: No frames on the current call stack
  main[1] run
  > stop at com.example.boot.controller.DebugController:19
Set breakpoint com.example.boot.controller.DebugController:19

Breakpoint hit: "thread=http-nio-8080-exec-2", com.example.boot.controller.DebugController.index(), line=19 bci=14

  http-nio-8080-exec-2[1] print port
 port = 60249

vscode attach

vscode中的launch.json内容如下，在DebugController第19行打上断点，按F5运行程序，访问http://localhost:8080/index即可进入断点。

{
    "version": "0.2.0",
    "configurations": [
        {
            "type": "java",
            "name": "Debug (Attach) SpringBootDebugApplication",
            "request": "attach",
            "hostName": "localhost",
            "port": 8000
        }
    ]
}

mvnDebug exec:java -Dstart-class="..."

 mvnDebug exec:java -Dstart-class="com.example.boot.SpringBootDebugApplication"
Preparing to execute Maven in debug mode
Listening for transport dt_socket at address: 8000

与前面一样，在jdb和vscode中是可以连接调试的，在IDEA中不行。

mvn spring-boot:run -Drun.jvmArguments="-agentlib:jdwp=..."

官方文档推荐使用插件spring-boot-maven-plugin的目标spring-boot:run运行spring-boot应用，如果有设置jvmArguments参数，就会自动派生新的 Java 进程来运行spring-boot中的main方法，所以可以用-Drun.jvmArguments把参数传给派生的 Java 进程，如下示例。

 mvn spring-boot:run -Drun.jvmArguments="-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=8000"
[INFO] Scanning for projects...
[INFO]
[INFO] ----------------< com.example.spring:spring-boot-debug >----------------
[INFO] Building spring-boot-debug 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] >>> spring-boot-maven-plugin:1.5.9.RELEASE:run (default-cli) > test-compile @ spring-boot-debug >>>
[INFO]
[INFO] --- spring-boot-maven-plugin:1.5.9.RELEASE:build-info (default) @ spring-boot-debug ---
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ spring-boot-debug ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 0 resource
[INFO] Copying 0 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ spring-boot-debug ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ spring-boot-debug ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /test/spring-boot-debug/src/test/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ spring-boot-debug ---
[INFO] No sources to compile
[INFO]
[INFO] <<< spring-boot-maven-plugin:1.5.9.RELEASE:run (default-cli) < test-compile @ spring-boot-debug <<<
[INFO]
[INFO]
[INFO] --- spring-boot-maven-plugin:1.5.9.RELEASE:run (default-cli) @ spring-boot-debug ---
[INFO] Attaching agents: []
Listening for transport dt_socket at address: 8000

程序启动的前一部分[INFO]日志是由主进程输出的，派生的子进程启动spring-boot应用，因为调试参数suspend=y，因此在8000端口等待客户端连接，这时一共启动了2个 Java 进程，如下所示，其中84974这个进程就是84952这个进程fork出来的子进程：

 ps -ef | grep java
  501 84952  1177   0 11:15PM ttys001    0:07.06 /Library/Java/JavaVirtualMachines/jdk1.8.0_77.jdk/Contents/Home/bin/java -classpath /usr/local/Cellar/maven/3.5.3/libexec/boot/plexus-classworlds-2.5.2.jar -Dclassworlds.conf=/usr/local/Cellar/maven/3.5.3/libexec/bin/m2.conf -Dmaven.home=/usr/local/Cellar/maven/3.5.3/libexec -Dlibrary.jansi.path=/usr/local/Cellar/maven/3.5.3/libexec/lib/jansi-native -Dmaven.multiModuleProjectDirectory=/github.com/test/spring-boot-debug org.codehaus.plexus.classworlds.launcher.Launcher spring-boot:run -Drun.jvmArguments=-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=8000
  501 84974 84952   0 11:15PM ttys001    0:00.07 /Library/Java/JavaVirtualMachines/jdk1.8.0_77.jdk/Contents/Home/jre/bin/java -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=8000 -cp /test/spring-boot-debug/target/classes:...:~/.m2/repository/com/fasterxml/jackson/core/jackson-databind/2.8.10/jackson-databind-2.8.10.jar com.example.boot.SpringBootDebugApplication

jdb attach

 jdb -attach 8000
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
Initializing jdb ...
>
VM Started: No frames on the current call stack

  main[1] stop at com.example.boot.controller.DebugController:19
Deferring breakpoint com.example.boot.controller.DebugController:19.
It will be set after the class is loaded.
  main[1] run
> Set deferred breakpoint com.example.boot.controller.DebugController:19

Breakpoint hit: "thread=http-nio-8080-exec-2", com.example.boot.controller.DebugController.index(), line=19 bci=14

  http-nio-8080-exec-2[1] print host
 host = "0:0:0:0:0:0:0:1"
  http-nio-8080-exec-2[1] print port
 port = 58781
  http-nio-8080-exec-2[1] print httpServletRequest
 httpServletRequest = "org.apache.catalina.connector.RequestFacade@7d5cdff"
  http-nio-8080-exec-2[1] print httpServletRequest.getHeader("user-agent")
 httpServletRequest.getHeader("user-agent") = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36"
  http-nio-8080-exec-2[1] cont

使用 IDEA 客户端连接

jdb与 IDE 相比还是不方便的，可以使用 IntelliJ IDEA 和 Eclipse 之类的工具进行 debug，vscode的调试功能也很不错，以IDEA为例，IDEA - Run - Attach to Local Process...，可以看到运行中的调试程序，点击连接之后，客户端提示如下，并且主程序会继续启动spring-boot应用。

Connected to the target VM, address: '127.0.0.1:8000', transport: 'socket'

java -cp "..." -agentlib:jdwp="..."

下面用最基本的java命令来启动main方法所在的应用程序进行调试。

在pom.xml文件所在目录下运行以下命令得到项目依赖的classpath，并将target/classes目录加入classpath中，然后运行main方法所在应用程序SpringBootDebugApplication：

 mvn dependency:build-classpath | grep -v "INFO\|WARN"
maven project classpath output here ......

 java -cp "target/classes:$(mvn dependency:build-classpath | grep -v "INFO\|WARN")" -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=8000 com.example.boot.SpringBootDebugApplication
Listening for transport dt_socket at address: 8000

然后用IDEA连接8000端口后开始调试代码。

spring-boot 2.0 参数变化

在spring-boot 2.x版本中，需要注意-Drun.jvmArguments被调整为-Dspring.boot.run.jvmArguments。

References

1. jdb - The Java Debugger
2. Spring Boot Maven Plugin