The pits encountered in the process of upgrading JDK17 from JDK8

1 Introduction

Although JDK8 is very good, the JDK version has been released to JDK20, and the version after JDK8 has been upgraded with many new features, such as modularization, ZGC, virtual threads, structural concurrency, etc., which are also very attractive, so I decided to use Projects based on JDK8 are upgraded to the latest LTS release, JDK17.

2 Upgrade process records

2.1 Install JDK17

Download the latest version of JDK17 jdk-17_linux-x64_bin.tar.gz, unzip it and move it to /usr/lib/jvm/the directory

$ sudo su -
# tar -xzf jdk-17_linux-x64_bin.tar.gz
# mv jdk-17.0.2 /usr/lib/jvm/java-17
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Then modify ~/.bashrcand set the java related environment variable to JDK17

# vim ~/.bashrc

export JAVA_HOME=/usr/lib/jvm/java-17
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH
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After the environment variable takes effect, check that the current jdk version is JDK17

# source ~/.bashrc

# java -version
openjdk version "17.0.2" 2022-01-18
OpenJDK Runtime Environment (build 17.0.2+8-86)
OpenJDK 64-Bit Server VM (build 17.0.2+8-86, mixed mode, sharing)
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2.2 Upgrade the spring version and compile

Modify the project pom.xmlfile, change the spring boot and spring cloud version by

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.12.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    
    <properties>
        <spring-cloud.version>Greenwich.SR3</spring-cloud.version>
    </properties>
    
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Modify to the latest official release version:

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.0.6</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    
    <properties>
        <spring-cloud.version>2022.0.2</spring-cloud.version>
    </properties>
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Compile the project and report the following error:

程序包javax.servlet.http不存在
程序包javax.validation不存在
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The reason is that the name of the original javaxpackage has been changed , replacing all dependent packages jakartain the project withjavaxjakarta

Continue to compile and report the following error:

[ERROR] 找不到符号
[ERROR]   符号:   类 EnableEurekaClient
[ERROR]   位置: 程序包 org.springframework.cloud.netflix.eureka
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The reason is that the new version has no @EnableEurekaClientannotations and is replaced by@EnableDiscoveryClient

Continue to compile and report the following error:

[ERROR]  找不到符号
[ERROR]   符号:   方法 apply()
[ERROR]   位置: 接口 io.github.resilience4j.core.functions.CheckedSupplier<java.lang.Object>
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The reason is resilience4jthat CheckedSupplierthe new version of the interface has no apply()method, so change it to get()method

Continue to compile and report the following error:

[ERROR]  对于RetryableException(int,java.lang.String,feign.Request.HttpMethod,java.util.Date), 找不到合适的构造器
[ERROR]     构造器 feign.RetryableException.RetryableException(int,java.lang.String,feign.Request.HttpMethod,java.lang.Throwable,java.util.Date,feign.Request)不适用
[ERROR]       (实际参数列表和形式参数列表长度不同)
[ERROR]     构造器 feign.RetryableException.RetryableException(int,java.lang.String,feign.Request.HttpMethod,java.util.Date,feign.Request)不适用
[ERROR]       (实际参数列表和形式参数列表长度不同)
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The reason is that the constructor openfeignof the new version of RetryableExceptionthe exception class has changed, and the old code is changed as needed:

    @Bean
    public ErrorDecoder feignError() {
        return (key, response) -> {
            if (response.status() >= 500) {
                FeignException exception = FeignException.errorStatus(key, response);
                return new RetryableException(
                        response.status(),
                        exception.getMessage(),
                        response.request().httpMethod(),
                        new Date());
            }

            // 其他异常交给Default去解码处理
            return defaultErrorDecoder.decode(key, response);
        };
    }

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Change to the following code

    @Bean
    public ErrorDecoder feignError() {
        return (key, response) -> {
            if (response.status() >= 500) {
                FeignException exception = FeignException.errorStatus(key, response);
                return new RetryableException(
                        response.status(),
                        exception.getMessage(),
                        response.request().httpMethod(),
                        new Date(),
                        response.request());
            }

            // 其他异常交给Default去解码处理
            return defaultErrorDecoder.decode(key, response);
        };
    }
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After changing to continue compiling, the following error is reported:

程序包org.junit不存在
程序包org.junit.runner不存在
程序包junit.framework不存在
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This is because older versions used the junit4corresponding junit5annotations. Coming soon:

import org.junit.Before;
import org.junit.Ignore;
import org.junit.Test;
import org.junit.runner.RunWith;

@Ignore
@RunWith(MockitoJUnitRunner.class)
public class FileSyncerTest {
    
    @Before
    public void setUp() {

    }
    
    @Test
    public void testCase1() throws Exception {
    
    }

}
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changed to

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.junit.jupiter.MockitoExtension;


@Disabled
@ExtendWith(MockitoExtension.class)
public class FileSyncerTest {
    
    @BeforeEach
    public void setUp() {

    }
    
    @Test
    public void testCase1() throws Exception {
    
    }

}

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Continue to compile after changing it, and the compilation passes.

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 8.582 s (Wall Clock)
[INFO] Finished at: 2023-05-04T16:39:42+08:00
[INFO] Final Memory: 59M/214M
[INFO] ------------------------------------------------------------------------
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2.3 Start the project

Start the project after the compilation is passed, but the startup fails and the following error is reported:

Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain) throws java.lang.ClassFormatError accessible: module java.base does not "opens java.lang" to unnamed module @7634b327
	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354)
	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
	at java.base/java.lang.reflect.Method.checkCanSetAccessible(Method.java:199)
	at java.base/java.lang.reflect.Method.setAccessible(Method.java:193)
	at net.sf.cglib.core.ReflectUtils$2.run(ReflectUtils.java:56)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:318)
	at net.sf.cglib.core.ReflectUtils.<clinit>(ReflectUtils.java:46)
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这是因为从JDK9开始支持模块化了，项目中使用的部分组件可能还没有支持模块化，所以需要在jar包启动时添加add-opens jvm启动参数参数，我是通过在pom文件中添加build参数实现的：

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <!-- 添加 add-opens jvm参数 -->
                    <jvmArguments>--add-opens java.base/java.lang=ALL-UNNAMED</jvmArguments>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>
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修改完后重新编译启动，启动仍然失败，报以下错误：

org.springframework.context.ApplicationContextException: Failed to start bean 'documentationPluginsBootstrapper'; nested exception is java.lang.NullPointerException
Caused by: java.lang.NullPointerException: null
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这是因为项目中使用了knife4j，由于版本比较低，底层依赖的是spring-fox，支持的是openapi 2.x版本，而spring boot 3.0只支持openapi 3.x版本，所以knife4j版本依赖由：

    <dependency>
        <groupId>com.github.xiaoymin</groupId>
        <artifactId>knife4j-spring-boot-starter</artifactId>
        <version>2.0.5</version>
    </dependency>
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改为：

    <dependency>
        <groupId>com.github.xiaoymin</groupId>
        <artifactId>knife4j-openapi3-jakarta-spring-boot-starter</artifactId>
        <version>4.1.0</version>
    </dependency>
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同时将swagger的相关注解@Api、@ApiOperation、@ApiParam、@ApiModel 、@ApiModelProperty替换为openapi3对应的注解：@Tag、@Operation、 @Parameter、 @Schema、 @SchemaProperty

修改完后，重新编译启动，这次能正常启动了

但是web访问项目接口时报以下错误：

Caused by: java.lang.IllegalArgumentException: When allowCredentials is true, allowedOrigins cannot contain the special value "*" since that cannot be set on the "Access-Control-Allow-Origin" response header. To allow credentials to a set of origins, list them explicitly or consider using "allowedOriginPatterns" instead.
	at org.springframework.web.cors.CorsConfiguration.validateAllowCredentials(CorsConfiguration.java:516)
	at org.springframework.web.servlet.handler.AbstractHandlerMapping.getHandler(AbstractHandlerMapping.java:538)
	at org.springframework.web.servlet.DispatcherServlet.getHandler(DispatcherServlet.java:1275)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:974)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1011)
	... 36 common frames omitted

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这个是跨域的问题，新版本spring MVC的CorsRegistry已经没有allowedOrigin() 方法了，替换为新接口allowedOriginPatterns()即可，代码示例如下：

@Configuration
public class WebCorsConfig implements WebMvcConfigurer {

    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")
                .allowedOriginPatterns("*")
                .allowedMethods("GET", "HEAD", "POST", "PUT", "DELETE", "OPTIONS")
                .allowCredentials(true)
                .maxAge(3600)
                .allowedHeaders("*");
    }
}
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到此升级完成！