如何使用thymeleaf 生成mybatis 模板

朱雀 2021-02-12 09:48 637阅读 0赞

## 如何使用thymeleaf 生成mybatis 模板 ##

**技术背景**  
我们在使用mybatis做数据库访问的时候,有很多重复的东西要写,如DAO里面的增删改查,mapper/provider里面的各种东东,还有实体类,其实这些都是可以通过名称关联起来的,因此就有这么一个需求,去写一个工具类,根据模板去生成这些文件

**以前的解决方案及问题**  
以前公司里面有前辈写过用的是beetl做的模板处理,没什么问题,之所以改用thymeleaf原因有以下两点: 1. thymeleaf是springboot官方指定模板处理 2. 想别的项目都依赖于这个工具包,所以工具包的依赖要尽可能少,在web应用已经引入了thymeleaf的前提下,尽可能不再引包了

**引入依赖**  
gradle:

compile group: ‘org.thymeleaf’, name: ‘thymeleaf’, version: ‘3.0.11.RELEASE’  
compile group: ‘ognl’, name: ‘ognl’, version: ‘3.2.10’  
maven:

org.thymeleaf thymeleaf 3.0.11.RELEASE ognl ognl 3.2.10 配置Thymeleaf 
````
public class TplConfig {

/**
     * 使用静态内部类的方式来实现单例模式
     */
    static class InitTplConfig{
        final static TemplateEngine templateEngine = new TemplateEngine();
        static TemplateEngine getEngine(){
            return templateEngine;
        }
    }
    
    /**
     * 别的地方想使用templateEngine来处理模板,调用这个方法来获取
     * @return
     */
    public static TemplateEngine getTemplateEngine() {
        final TemplateEngine templateEngine = InitTplConfig.getEngine();
        // 处理txt的
        templateEngine.addTemplateResolver(textTemplateResolver());
    
        return templateEngine;
    }
    
    
    /**
     * 配置模板的位置,前缀,后缀等
     * @return
     */
    private static ITemplateResolver textTemplateResolver() {
        final ClassLoaderTemplateResolver templateResolver = new ClassLoaderTemplateResolver();
        templateResolver.setOrder(1);
        templateResolver.setResolvablePatterns(Collections.singleton("text/*"));
        templateResolver.setPrefix("/tpl/");
        templateResolver.setSuffix(".txt");
        templateResolver.setTemplateMode(TemplateMode.TEXT);
        templateResolver.setCharacterEncoding("UTF-8");
        templateResolver.setCacheable(false);
        return templateResolver;
    }

}  
````
与此同时,对应的项目结构为:

获取数据库表的相关信息  
这块有两种方式: 1. 通过jdbc的方式,比较传统,注册驱动,获取连接等等 2. 直接注入datasource,然后通过datasource.getConnection获取连接,因为现在开发基本上都是spring环境,本文采用第2种方式

/** 存数据库类型和java类型的映射 */  
````
private Map<String,String> property2BeanMap = new HashMap<>();

public MybatisGenerateUtils(DataSource dataSource) {
        this.dataSource = dataSource;
        property2BeanMap.put("BIGINT UNSIGNED","Long");
        property2BeanMap.put("DATETIME","Date");
        property2BeanMap.put("TIMESTAMP","Date");
        property2BeanMap.put("VARCHAR","String");
        property2BeanMap.put("DECIMAL","BigDecimal");
        property2BeanMap.put("BIGINT","Long");
        property2BeanMap.put("TEXT","String");
        property2BeanMap.put("TINYINT","Integer");
        property2BeanMap.put("INT","Integer");
        property2BeanMap.put("BIT","Integer");
        property2BeanMap.put("CHAR","String");
    }

/**  
* 获取mysql里面的表信息,读取表里面所有字段,  
* 并封到java实体类里面  
*  
* @param tableName  
* @return  
*/  
public SqlTable getTableInfo(String dbName, String tableName) {

SqlTable table = new SqlTable();

//把tableName转成驼峰式,并且首子母改成大写  
String javaTableName = StringUtils.first2BigLetter(StringUtils.underScope2Camel(tableName));  
table.setTableName(tableName).setJavaTableName(javaTableName);  
Connection conn = null;  
try {  
conn = dataSource.getConnection();

DatabaseMetaData metaData = conn.getMetaData();
            ResultSet resultSet = metaData.getColumns(null, null, tableName, "%");
            String columnName;
            String columnType;
    
            List<SqlField> fieldList = new ArrayList<>();
            while (resultSet.next()) {
                if (!resultSet.getString("TABLE_CAT").equals(dbName)) {
                    continue;
                }
                SqlField field = new SqlField();
                columnName = resultSet.getString("COLUMN_NAME");
                columnType = resultSet.getString("TYPE_NAME");
                String remark = resultSet.getString("REMARKS");
                field.setName(columnName).setRemark(remark).setType(columnType);
                field.setCamelName(StringUtils.underScope2Camel(columnName));
        field.setJavaType(property2BeanMap.get(columnType));
                fieldList.add(field);
            }
            table.setFieldList(fieldList).setTableName(tableName);
        } catch (SQLException ex) {
            ex.printStackTrace();
        }
        return table;
    }
````
SqlTable.java内容如下:

/** 表名 */
    private String tableName;

/** 对应的java实体类的名称 */
    private String javaTableName;
    
    /** 表里面的字段名 */
    private List<SqlField> fieldList;

SqlField.java内容如下:

/**字段名称*/  
    private String name;

/**驼蜂式命名*/
    private String camelName;
    
    /**字段类型*/
    private String type;
    
    /**java实体类的类型*/
    private String javaType;
    
    /**备注*/
    private String remark;
    
    /** 数据库类型 */
    private String jdbcType;

数据库的模板文件如下:
````
package com.platform.forest.models;

/**

*  @author lixiang  
    */  
    public class [(${table.javaTableName})]DO {
    
    [# th:each="field :  t a b l e . f i e l d L i s t " ] / ∗ ∗ [ ( {table.fieldList}"] /** [( table.fieldList"]/∗∗[({field.remark})] */  
    private [( f i e l d . j a v a T y p e ) ] [ ( {field.javaType})] [( field.javaType)][({field.camelName})];
    
    [/]
    
    /**
    
     *  这两个方法是用建设者模式来build DO  
        */  
        public static [(KaTeX parse error: Expected '}', got 'EOF' at end of input: … return new [({table.javaTableName})]DO();  
        }
    
    public [(${table.javaTableName})]DO build(){  
    return this;  
    }

}
````
**最后的调用**

推荐这些使用单元测试的方式来生成这些东东
````
public class MybatisTests extends ToolsApplicationTests {

@Autowired
    private DataSource dataSource;
    
    @Test
    public void testGenerate() {
        //获取数据库信息
        MybatisGenerateUtils utils = new MybatisGenerateUtils(dataSource);
        SqlTable tableInfo = utils.getTableInfo("passport", "role");
        //初始化thymeleaf
        TemplateEngine engine = TplConfig.getTemplateEngine();
        final Context ctx = new Context(Locale.CHINA);
        Map<String, Object> map = new HashMap<>();
        map.put("table",tableInfo);
        ctx.setVariables(map);
        String process = engine.process("text/mybatis/mysql-model.txt", ctx);
        System.out.println(process);
    }

}
````