如何使用freemarker编写代码生成器

雨点打透心脏的1/2处 2022-12-15 06:17 177阅读 0赞

pom.xml文件引入freemarker和jdbc依赖

<dependency>
          <groupId>org.freemarker</groupId>
          <artifactId>freemarker</artifactId>
          <version>2.3.16</version>
        </dependency>
        <dependency>
          <groupId>mysql</groupId>
          <artifactId>mysql-connector-java</artifactId>
          <version>5.1.22</version>
    </dependency>

模板文件module.ftl, 所在位置classpath下的module中

package cn.code.bean;
     
    public class ${myClass.className} { 
     
        <#list myClass.fieldList as field>
            //${field.fieldRemarks}
            private ${field.fieldType} ${field.fieldName};
        </#list>
     
        <#list myClass.fieldList as field>
            public ${field.fieldType} get${field.fieldNameUpperFirstLetter}() { 
                return ${field.fieldName};
            }
     
            public void set${field.fieldNameUpperFirstLetter}(${field.fieldType} ${field.fieldName}) { 
                this.${field.fieldName} = ${field.fieldName};
            }
        </#list>
    }

属性类Field.class
    
    package cn.code.generate;
     
    //属性类
    
    ```java
    public class Field { 
        //字段名
        private String fieldName;
        //字段类型
        private String fieldType;
        //字段注释
        private String fieldRemarks;
        //字段名首字母大写
        private String fieldNameUpperFirstLetter;
     
        public String getFieldName() { 
            return fieldName;
        }
     
        public void setFieldName(String fieldName) { 
            this.fieldName = fieldName;
        }
     
        public String getFieldType() { 
            return fieldType;
        }
     
        public void setFieldType(String fieldType) { 
            this.fieldType = fieldType;
        }
     
        public String getFieldRemarks() { 
            return fieldRemarks;
        }
     
        public void setFieldRemarks(String fieldRemarks) { 
            this.fieldRemarks = fieldRemarks;
        }
     
        public String getFieldNameUpperFirstLetter() { 
            return fieldNameUpperFirstLetter;
        }
     
        public void setFieldNameUpperFirstLetter(String fieldNameUpperFirstLetter) { 
            this.fieldNameUpperFirstLetter = fieldNameUpperFirstLetter;
        }
    }

MyClass.java

package cn.code.generate;
     
    import java.util.List;
     
    public class MyClass { 
        //类名
        private String className;
        //字段的集合
        private List<Field> fieldList;
     
        public String getClassName() { 
            return className;
        }
     
        public void setClassName(String className) { 
            this.className = className;
        }
     
        public List<Field> getFieldList() { 
            return fieldList;
        }
     
        public void setFieldList(List<Field> fieldList) { 
            this.fieldList = fieldList;
        }
    }

ClassGenerator.class

package cn.code.generate;
     
    import java.sql.Connection;
    import java.sql.DatabaseMetaData;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.util.ArrayList;
    import java.util.List;
     
    public class ClassGenerator { 
     
        public DatabaseMetaData init(){ 
            DatabaseMetaData databaseMetaData = null;
            try{ 
                Class.forName("com.mysql.jdbc.Driver");
                String url = "jdbc:mysql://192.168.126.133:3306/itrip";
                String user = "root";
                String password = "123456";
                Connection connection = DriverManager.getConnection(url, user, password);
                databaseMetaData = connection.getMetaData();
            }catch (Exception e){ 
                e.printStackTrace();
            }
            return databaseMetaData;
        }
     
        //根据表名生产出类
        public MyClass generateClass(String tableName){ 
            MyClass myClass = new MyClass();
            List<Field> fieldList = new ArrayList<Field>();
            DatabaseMetaData databaseMetaData = init();
            try{ 
                ResultSet rs = databaseMetaData.getColumns(null, "%", tableName, "%");
                while(rs.next()){ 
                    //列名
                    String columnName = rs.getString("COLUMN_NAME");
                    //类型
                    String typeName = rs.getString("TYPE_NAME");
                    System.out.println("typeName:" + typeName);
                    //注释
                    String remarks = rs.getString("REMARKS");
     
                    Field field = new Field();
                    field.setFieldName(columnName);
                    field.setFieldType(columnTypeToFieldType(typeName));
                    field.setFieldRemarks(remarks);
                    field.setFieldNameUpperFirstLetter(upperFirstLetter(columnName));
                    fieldList.add(field);
                }
            }catch (Exception e){ 
                e.printStackTrace();
            }
     
            myClass.setClassName(tableNameToClassName(tableName));
            myClass.setFieldList(fieldList);
     
            return myClass;
        }
     
        //字段类型转换成属性类型
        public String columnTypeToFieldType(String columnType){ 
            String fieldType = null;
            switch (columnType) { 
                case "INT":
                    fieldType = "Integer";
                    break;
                case "VARCHAR":
                    fieldType = "String";
                    break;
                case "CHAR":
                    fieldType = "String";
                    break;
                case "DATE":
                    fieldType = "Date";
                    break;
                case "BIGINT":
                    fieldType = "Long";
                    break;
                default:
                    fieldType = "String";
                    break;
            }
            return fieldType;
        }
     
        //首字母大写
        public String upperFirstLetter(String src){ 
            String firstLetter = src.substring(0, 1).toUpperCase();
            String otherLetters = src.substring(1);
            return firstLetter + otherLetters;
        }
     
        //表名转类名
        public String tableNameToClassName(String tableName){ 
            StringBuilder className = new StringBuilder();
            //aa_bb_cc AaBbCc
            String[] split = tableName.split("_");
            for (String item : split) { 
                className.append(upperFirstLetter(item));
            }
            return className.toString();
        }
    }

Generator.class

package cn.code.generate;
     
    import cn.code.User;
    import freemarker.template.Configuration;
    import freemarker.template.Template;
     
    import java.io.File;
    import java.io.FileOutputStream;
    import java.io.OutputStreamWriter;
    import java.io.Writer;
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
     
    public class Generator { 
     
        public static void main(String[] args) throws Exception{ 
            //创建Configuration对象
            Configuration configuration = new Configuration();
            //设置模板所在目录
            String path = Generator.class.getClassLoader().getResource("module").getPath();
            configuration.setDirectoryForTemplateLoading(new File(path));
            //获取模板
            Template template = configuration.getTemplate("class.ftl");
            //设置数据并执行
            Map map = new HashMap();
     
            ClassGenerator classGenerator = new ClassGenerator();
            MyClass myClass = classGenerator.generateClass("user");
     
            map.put("myClass", myClass);
     
            Writer writer = new OutputStreamWriter(new FileOutputStream("G:/"+myClass.getClassName()+".java"));
     
            template.process(map, writer);
        }
    }

转自：https://blog.csdn.net/fengqing5578/article/details/80335043