封装与职责分离的开发思维

@Override
    public List<Teacher> query(String name, Integer minAge, Integer maxAge, Integer dormBuildId) {
        StringBuilder sql = new StringBuilder();
        sql.append("SELECT * FROM t_teacher WHERE 1=1");
        //封装占位符参数
        List<Object> parameters = new ArrayList<>();
        //拼接sql和设置占位符参数值　　    //姓名
        if (StringUtils.isNotBlank(name)) {
            sql.append(" AND name LIKE ?");
            parameters.add("%" + name + "%");
        }
        //最小年龄
        if(minAge != null) {
            sql.append(" AND age >= ?");
            parameters.add(minAge);
        }        
        //最大年龄
        if(maxAge != null) {
            sql.append(" AND age <= ?");
            parameters.add(maxAge);
        }
        System.out.println("sql=" + sql);
        System.out.println("parameters=" + parameters);
        return JdbcTemplate.query(sql.toString(), new BeanListHandler<>(Teacher.class), parameters.toArray());
    }

package com.shan.query;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.lang3.StringUtils;
import lombok.Data;
@Data
public class TeacherQueryObject {
    private String name;
    private Integer minAge;
    private Integer maxAge;
    private Integer dormBuildId;
//    // 封装占位符参数
    private List<Object> parameters = new ArrayList<>();
    public TeacherQueryObject() {};
    public TeacherQueryObject(String name, Integer minAge, Integer maxAge, Integer dormBuildId) {
        this.name = name;
        this.minAge = minAge;
        this.maxAge = maxAge;
        this.dormBuildId = dormBuildId;
        this.parameters = parameters;
    }
    public String getQuery() {
        StringBuilder sql = new StringBuilder();
        sql.append(" WHERE 1=1");
        // 拼接姓名
        if (StringUtils.isNotBlank(name)) {
            sql.append(" AND name LIKE ?");        
            parameters.add("%" + name + "%");
        }
        // 拼接最小年龄
        if (minAge != null) {
            sql.append(" AND age >= ?");    
            parameters.add(minAge);
        }
        // 拼接最大年龄
        if (maxAge != null) {
            sql.append(" AND age <= ?");
            parameters.add(maxAge);
        }
        return sql.toString();
    }
    public List<Object> getParameters() {
        return parameters;
    }
}

// 高级查询
    @Override
    public List<Teacher> query(TeacherQueryObject tqo) {
        //职责分离【要拼接的sql语句的数据时在tqo对象里的，且占位符的参数设置数据也是在tqo对象，则tqo对象应该提供对应的方法】
        String querySql = tqo.getQuery();
        String sql = "select * from t_teacher" + querySql;
        List<Object> parameters = tqo.getParameters();
        System.out.println(querySql);
        System.out.println(parameters);
        return JdbcTemplate.query(sql, new BeanListHandler<>(Teacher.class), parameters.toArray());
    }