MyBatis —— 代码生成器实践

骑猪看日落 2022-01-14 10:15 217阅读 0赞

**目录**

1、创建 generatorConfig.xml 文件

2、创建自定义注释类

3、创建自定义类型转换类

4、创建运行类Generator

5、创建MySQL数据源，如配置中所示

6、运行Generator类

7、总结

--------------------

# 1、创建 generatorConfig.xml 文件 #

在src/main/resources 下创建 generator 目录，创建 generatorConfig.xml 文件

内容如下：

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE generatorConfiguration
            PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
            "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
    
    <generatorConfiguration>
        
        
        <context id="MysqlContext" targetRuntime="MyBatis3Simple" defaultModelType="flat">
            
            <property name="beginningDelimiter" value="`"/>
            <property name="endingDelimiter" value="`"/>
            
            <commentGenerator type="rh.study.mybatis.generator.MyCommentGenerator"/>
    
            <jdbcConnection driverClass="com.mysql.jdbc.Driver"
                            connectionURL="jdbc:mysql://localhost:3306/knowledge"
                            userId="root"
                            password="root">
            </jdbcConnection>
    
            <javaTypeResolver type="rh.study.mybatis.generator.MyJavaTypeResolver"/>
    
            
            <javaModelGenerator targetPackage="test.model" targetProject="src\main\java">
                
                <property name="trimStrings" value="true" />
            </javaModelGenerator>
            
            <sqlMapGenerator targetPackage="test.dao"  targetProject="src\main\resources"/>
            
            <javaClientGenerator type="XMLMAPPER" targetPackage="test.dao"  targetProject="src\main\java"/>
    
            <table tableName="%">
                <generatedKey column="id" sqlStatement="Mysql"/>
            </table>
        </context>
    </generatorConfiguration>

# 2、创建自定义注释类 #

package rh.study.mybatis.generator;
    
    import org.mybatis.generator.api.IntrospectedColumn;
    import org.mybatis.generator.api.IntrospectedTable;
    import org.mybatis.generator.api.dom.java.*;
    import org.mybatis.generator.api.dom.xml.XmlElement;
    import org.mybatis.generator.config.MergeConstants;
    import org.mybatis.generator.config.PropertyRegistry;
    import org.mybatis.generator.internal.DefaultCommentGenerator;
    
    import java.text.SimpleDateFormat;
    import java.util.Date;
    import java.util.Properties;
    
    import static org.mybatis.generator.internal.util.StringUtility.isTrue;
    
    /**
     * 自定义生成注释类
     */
    public class MyCommentGenerator extends DefaultCommentGenerator {
        private Properties properties;
        private Properties systemPro;
        private boolean suppressDate;
        private boolean suppressAllComments;
        private String currentDateStr;
    
        public MyCommentGenerator() {
            super();
            properties = new Properties();
            systemPro = System.getProperties();
            suppressDate = false;
            suppressAllComments = false;
            currentDateStr = (new SimpleDateFormat("yyyy-MM-dd")).format(new Date());
        }
    
        @Override
        public void addJavaFileComment(CompilationUnit compilationUnit) {
            // add no file level comments by default
            return;
        }
    
        /**
         * Adds a suitable comment to warn users that the element was generated, and
         * when it was generated.
         */
        @Override
        public void addComment(XmlElement xmlElement) {
            return;
        }
    
        @Override
        public void addRootComment(XmlElement rootElement) {
            // add no document level comments by default
            return;
        }
    
        @Override
        public void addConfigurationProperties(Properties properties) {
            this.properties.putAll(properties);
    
            suppressDate = isTrue(properties.getProperty(PropertyRegistry.COMMENT_GENERATOR_SUPPRESS_DATE));
    
            suppressAllComments = isTrue(properties.getProperty(PropertyRegistry.COMMENT_GENERATOR_SUPPRESS_ALL_COMMENTS));
        }
    
        /**
         * This method adds the custom javadoc tag for. You may do nothing if you do
         * not wish to include the Javadoc tag - however, if you do not include the
         * Javadoc tag then the Java merge capability of the eclipse plugin will
         * break.
         *
         * @param javaElement the java element
         */
        protected void addJavadocTag(JavaElement javaElement, boolean markAsDoNotDelete) {
            javaElement.addJavaDocLine(" *");
            StringBuilder sb = new StringBuilder();
            sb.append(" * ");
            sb.append(MergeConstants.NEW_ELEMENT_TAG);
            if (markAsDoNotDelete) {
                sb.append(" do_not_delete_during_merge");
            }
            String s = getDateString();
            if (s != null) {
                sb.append(' ');
                sb.append(s);
            }
            javaElement.addJavaDocLine(sb.toString());
        }
    
        /**
         * This method returns a formated date string to include in the Javadoc tag
         * and XML comments. You may return null if you do not want the date in
         * these documentation elements.
         *
         * @return a string representing the current timestamp, or null
         */
        protected String getDateString() {
            String result = null;
            if (!suppressDate) {
                result = currentDateStr;
            }
            return result;
        }
    
        @Override
        public void addClassComment(InnerClass innerClass, IntrospectedTable introspectedTable) {
            if (suppressAllComments) {
                return;
            }
            StringBuilder sb = new StringBuilder();
            innerClass.addJavaDocLine("/**");
            sb.append(" * ");
            sb.append(introspectedTable.getFullyQualifiedTable());
            sb.append(" ");
            sb.append(getDateString());
            innerClass.addJavaDocLine(sb.toString().replace("\n", " "));
            innerClass.addJavaDocLine(" */");
        }
    
        @Override
        public void addEnumComment(InnerEnum innerEnum, IntrospectedTable introspectedTable) {
            if (suppressAllComments) {
                return;
            }
            StringBuilder sb = new StringBuilder();
            innerEnum.addJavaDocLine("/**");
            sb.append(" * ");
            sb.append(introspectedTable.getFullyQualifiedTable());
            innerEnum.addJavaDocLine(sb.toString().replace("\n", " "));
            innerEnum.addJavaDocLine(" */");
        }
    
        @Override
        public void addFieldComment(Field field, IntrospectedTable introspectedTable,
                                    IntrospectedColumn introspectedColumn) {
            if (suppressAllComments) {
                return;
            }
            StringBuilder sb = new StringBuilder();
            field.addJavaDocLine("/**");
            sb.append(" * ");
            sb.append(introspectedColumn.getRemarks());
            field.addJavaDocLine(sb.toString().replace("\n", " "));
            field.addJavaDocLine(" */");
        }
    
        @Override
        public void addFieldComment(Field field, IntrospectedTable introspectedTable) {
            if (suppressAllComments) {
                return;
            }
            StringBuilder sb = new StringBuilder();
            field.addJavaDocLine("/**");
            sb.append(" * ");
            sb.append(introspectedTable.getFullyQualifiedTable());
            field.addJavaDocLine(sb.toString().replace("\n", " "));
            field.addJavaDocLine(" */");
        }
    
        @Override
        public void addGeneralMethodComment(Method method, IntrospectedTable introspectedTable) {
            if (suppressAllComments) {
                return;
            }
            method.addJavaDocLine("/**");
            addJavadocTag(method, false);
            method.addJavaDocLine(" */");
        }
    
        @Override
        public void addGetterComment(Method method, IntrospectedTable introspectedTable,
                                     IntrospectedColumn introspectedColumn) {
            if (suppressAllComments) {
                return;
            }
            method.addJavaDocLine("/**");
            StringBuilder sb = new StringBuilder();
            sb.append(" * ");
            sb.append(introspectedColumn.getRemarks());
            method.addJavaDocLine(sb.toString().replace("\n", " "));
            sb.setLength(0);
            sb.append(" * @return ");
            sb.append(introspectedColumn.getActualColumnName());
            sb.append(" ");
            sb.append(introspectedColumn.getRemarks());
            method.addJavaDocLine(sb.toString().replace("\n", " "));
            method.addJavaDocLine(" */");
        }
    
        @Override
        public void addSetterComment(Method method, IntrospectedTable introspectedTable,
                                     IntrospectedColumn introspectedColumn) {
            if (suppressAllComments) {
                return;
            }
            method.addJavaDocLine("/**");
            StringBuilder sb = new StringBuilder();
            sb.append(" * ");
            sb.append(introspectedColumn.getRemarks());
            method.addJavaDocLine(sb.toString().replace("\n", " "));
            Parameter parm = method.getParameters().get(0);
            sb.setLength(0);
            sb.append(" * @param ");
            sb.append(parm.getName());
            sb.append(" ");
            sb.append(introspectedColumn.getRemarks());
            method.addJavaDocLine(sb.toString().replace("\n", " "));
            method.addJavaDocLine(" */");
        }
    
        @Override
        public void addClassComment(InnerClass innerClass, IntrospectedTable introspectedTable, boolean markAsDoNotDelete) {
            if (suppressAllComments) {
                return;
            }
            StringBuilder sb = new StringBuilder();
            innerClass.addJavaDocLine("/**");
            sb.append(" * ");
            sb.append(introspectedTable.getFullyQualifiedTable());
            innerClass.addJavaDocLine(sb.toString().replace("\n", " "));
            sb.setLength(0);
            sb.append(" * @author ");
            sb.append(systemPro.getProperty("user.name"));
            sb.append(" ");
            sb.append(currentDateStr);
            innerClass.addJavaDocLine(" */");
        }
    }

# 3、创建自定义类型转换类 #

主要转换 smallint转为java的 Integer类型，decimal 转为java的 double 类型。

package rh.study.mybatis.generator;
    
    import org.mybatis.generator.api.dom.java.FullyQualifiedJavaType;
    import org.mybatis.generator.internal.types.JavaTypeResolverDefaultImpl;
    
    /**
     * 类型转换
     */
    public class MyJavaTypeResolver extends JavaTypeResolverDefaultImpl {
    
        public MyJavaTypeResolver() {
            super();
            super.typeMap.put(Integer.valueOf(5), new JavaTypeResolverDefaultImpl.JdbcTypeInformation("SMALLINT", new FullyQualifiedJavaType(Integer.class.getName())));
            super.typeMap.put(Integer.valueOf(-6), new JavaTypeResolverDefaultImpl.JdbcTypeInformation("TINYINT", new FullyQualifiedJavaType(Integer.class.getName())));
            super.typeMap.put(Integer.valueOf(3), new JavaTypeResolverDefaultImpl.JdbcTypeInformation("DECIMAL", new FullyQualifiedJavaType(Double.class.getName())));
        }
    }

# 4、创建运行类Generator #

package rh.study.mybatis.generator;
    
    import org.mybatis.generator.api.MyBatisGenerator;
    import org.mybatis.generator.config.Configuration;
    import org.mybatis.generator.config.xml.ConfigurationParser;
    import org.mybatis.generator.internal.DefaultShellCallback;
    
    import java.io.InputStream;
    import java.util.ArrayList;
    import java.util.List;
    
    /**
     *  读取 MBG配置生成代码
     */
    public class Generator {
    
        public static void main(String[] args) throws Exception{
            // MBG 执行过程中的警告信息
            List<String> warning = new ArrayList<>();
            // 当生成的代码重复时，覆盖原代码
            boolean overwrite = true;
            // 读取 MBG 配置
            InputStream in = Generator.class.getResourceAsStream("/generator/generatorConfig.xml");
            ConfigurationParser cp = new ConfigurationParser(warning);
            Configuration configuration = cp.parseConfiguration(in);
            in.close();
    
            DefaultShellCallback callback = new DefaultShellCallback(overwrite);
            // 创建 MBG
            MyBatisGenerator generator = new MyBatisGenerator(configuration, callback, warning);
            // 执行生成代码
            generator.generate(null);
            // 输出警告信息
            for (String w : warning) {
                System.out.println(w);
            }
        }
    
    }

# 5、创建MySQL数据源，如配置中所示 #

# 6、运行Generator类 #

运行结果如下，下图红色部分就是动态生成的代码

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3J1YW5oYW8xMjAz_size_16_color_FFFFFF_t_70][]

# 7、总结 #

以上只是简单的实践，具体配置信息的意思还要自己了解，多试几次就知道怎么用了

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