在 Java 中生成 JAXB 类时添加 toString、hashCode、equals [英] Add toString, hashCode, equals while generating JAXB classes in Java

问题描述

我正在尝试使用 Java 以编程方式从 XSD 文件生成 JAXB 类.我使用以下代码片段来实现这一点:

I'm trying to generate JAXB classes from an XSD file programmatically, using Java. I've used the following code snippet to achieve that:

....
import java.io.File;
import java.io.IOException;
import org.xml.sax.InputSource;
import com.sun.codemodel.JCodeModel;
import com.sun.tools.xjc.api.S2JJAXBModel;
import com.sun.tools.xjc.api.SchemaCompiler;
import com.sun.tools.xjc.api.XJC;
....
....
public static void generateJaxb(String schemaPath,
                                    String outputDirectory,
                                        String packageName) throws DataLoadingException
{
    try {
        // Setup schema compiler
        SchemaCompiler sc = XJC.createSchemaCompiler();
        sc.forcePackageName(packageName);

        // Setup SAX InputSource
        File schemaFile = new File(schemaPath);
        InputSource is = new InputSource(schemaFile.toURI().toString());

        // Parse & build
        sc.parseSchema(is);
        S2JJAXBModel model = sc.bind();

        JCodeModel jCodeModel = model.generateCode(null, null);
        jCodeModel.build(new File(outputDirectory));
    } catch (IOException exec) {
        LOGGER.error("Error while generating JAXB classes: " + exec);
    }
}

生成的类只包含字段的 getter 方法.但是，我还想包括 hashCode、equals 和 setter 方法.如何在生成代码时做到这一点?

The generated classes contain only the getter methods for the fields. But, I want to include the hashCode, equals and setter methods as well. How to do that while generating the code?

推荐答案

在 GitHub 网站上，您会找到 JAXB2 基础项目，它提供了一组通用的 JAXB 实用程序插件，其中包括 4 个应该解决您要实现的目标:

On the GitHub website, you will find the JAXB2 Basics project, which provides a common set of JAXB utility plugins, including 4 that should address what you are trying to achieve:

1. Equals 插件
2. HashCode 插件
3. Setters 插件
4. ToString 插件

还有其他插件可用，它们涵盖了 Java 域对象的类似常见方面.

There are other plugins available that cover similar common aspects of Java domain objects.

从 XML Schema 配置角度来看，您将添加如下所示的引用:

From an XML Schema configuration perspective, you will add references as shown here:

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
    xmlns:basic="http://jaxb2-commons.dev.java.net/basic"
    xmlns:equals="http://jaxb2-commons.dev.java.net/basic/equals"
    xmlns:hashCode="http://jaxb2-commons.dev.java.net/basic/hashCode"
    xmlns:toString="http://jaxb2-commons.dev.java.net/basic/toString"
    jaxb:extensionBindingPrefixes="basic equals hashCode toString">
    <!-- ... -->
</xs:schema>

还有其他可用选项，例如定义在生成 equals( that ) 实现、toString() 实现等时应忽略的对象属性.

There are additional options available, such as defining object properties that should be ignored when generating an equals( that ) implementation, a toString() implementation, etc.

从Java 的角度来看，插件通常让生成的类实现一个interface；例如，生成的包含 equals( that ) 实现的类将实现 [Equals][6] 接口.

From a Java perspective, the plugins generally have the generated classes implement an interface; as an example, generated classes that include an equals( that ) implementation will implement the [Equals][6] interface.

插件使用的设计方法通常会产生两种实现方式:

The design approach used by the plugins usually generates 2 flavors of implementation:

1. 简单/标准的实现，例如 equals( that ) 方法(使用 Equals 插件 时).
2. 更复杂的实现，包括 locator 和 strategy 参数，允许您实现自定义处理(如果您愿意).对于这些，您将看到一个方法签名，例如:equals(thisLocator, thatLocator, that, strategy).

1. A simple/standard implementation, such as an equals( that ) method (when using the Equals Plugin).
2. A more complex implementation that includes locator and strategy parameters, which allows you to implement custom handling (if you wish). For these, you will see a method signature such as: equals( thisLocator, thatLocator, that, strategy).

构建/运行时

从运行时的角度来看，您必须包含 JAXB2 Basics Runtime jar 并提供选项参数，例如:-Xequals、-XhashCode 或 -XtoString.提供了使用 Ant 和 Maven 中的 JAXB2 基础知识的示例，如果您使用其中任何一个来执行构建，并且 JAXB2 基础用户指南.

Build/Runtime

From a runtime perspective, you must include the JAXB2 Basics Runtime jar and provide option parameters such as: -Xequals, -XhashCode, or -XtoString. There are examples provided for using the JAXB2 Basics from Ant and Maven, if you are using either of those to perform builds and more build-related details are provided in the JAXB2 Basics User Guide.

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